Convert UTC GMT time to local time

Question

We are developing a C  application for a web-service client  This will run on Windows XP PC s   One of the fields returned by the web service is a DateTime field  The server returns a field in GMT format i e  with a  Z  at the end   However  we found that  NET seems to do some kind of implicit conversion and the time was always 12 hours out   The following code sample resolves this to some extent in that the 12 hour difference has gone but it makes no allowance for NZ daylight saving   CultureInfo ci   new CultureInfo  en-NZ    string date    Web service date  ToString  R   ci   DateTime convertedDate   DateTime Parse date                 As per this date site      UTC GMT Offset       Standard time zone  UTC GMT  12 hours   Daylight saving time   1 hour   Current time zone offset  UTC GMT  13 hours     How do we adjust for the extra hour  Can this be done programmatically or is this some kind of setting on the PC s

User · Answer

I came across this question as I was having a problem with the UTC dates you get back through the twitter API (created_at field on a status); I need to convert them to DateTime. None of the answers/ code samples in the answers on this page were sufficient to stop me getting a "String was not recognized as a valid DateTime" error (but it's the closest I have got to finding the correct answer on SO)

Posting this link here in case this helps someone else - the answer I needed was found on this blog post: http://www.wduffy.co.uk/blog/parsing-dates-when-aspnets-datetimeparse-doesnt-work/ - basically use DateTime.ParseExact with a format string instead of DateTime.Parse

User · Answer

DateTime objects have the Kind of Unspecified by default  which for the purposes of ToLocalTime is assumed to be UTC   To get the local time of an Unspecified DateTime object  you therefore just need to do this   convertedDate ToLocalTime      The step of changing the Kind of the DateTime from Unspecified to UTC is unnecessary  Unspecified is assumed to be UTC for the purposes of ToLocalTime  http   msdn microsoft com en-us library system datetime tolocaltime aspx

User · Answer

Don t forget if you already have a DateTime object and are not sure if it s UTC or Local  it s easy enough to use the methods on the object directly   DateTime convertedDate   DateTime Parse date   DateTime localDate   convertedDate ToLocalTime         How do we adjust for the extra hour    Unless specified  net will use the local pc settings  I d have a read of  http   msdn microsoft com en-us library system globalization daylighttime aspx  By the looks the code might look something like   DaylightTime daylight   TimeZone CurrentTimeZone GetDaylightChanges  year      And as mentioned above double check what timezone setting your server is on  There are articles on the net for how to safely affect the changes in IIS

User · Answer

I d look into using the System TimeZoneInfo class if you are in  NET 3 5  See http   msdn microsoft com en-us library system timezoneinfo aspx  This should take into account the daylight savings changes correctly      Coordinated Universal Time string from     DateTime Now ToUniversalTime   ToString  u    string date    2009-02-25 16 13 00Z       Local  NET timeZone  DateTime localDateTime   DateTime Parse date    DateTime utcDateTime   localDateTime ToUniversalTime        ID from       HKEY LOCAL MACHINE Software Microsoft Windows NT CurrentVersion Time Zone     See http   msdn microsoft com en-us library system timezoneinfo id aspx string nzTimeZoneKey    New Zealand Standard Time   TimeZoneInfo nzTimeZone   TimeZoneInfo FindSystemTimeZoneById nzTimeZoneKey   DateTime nzDateTime   TimeZoneInfo ConvertTimeFromUtc utcDateTime  nzTimeZone

User · Answer

For strings such as 2012-09-19 01 27 30 000  DateTime Parse cannot tell what time zone the date and time are from   DateTime has a Kind property  which can have one of three time zone options    Unspecified Local Utc   NOTE If you are wishing to represent a date time other than UTC or your local time zone  then you should use DateTimeOffset     So for the code in your question   DateTime convertedDate   DateTime Parse dateStr    var kind   convertedDate Kind     will equal DateTimeKind Unspecified   You say you know what kind it is  so tell it   DateTime convertedDate   DateTime SpecifyKind      DateTime Parse dateStr       DateTimeKind Utc    var kind   convertedDate Kind     will equal DateTimeKind Utc   Now  once the system knows its in UTC time  you can just call ToLocalTime   DateTime dt   convertedDate ToLocalTime      This will give you the result you require

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DateTime objects have the Kind of Unspecified by default  which for the purposes of ToLocalTime is assumed to be UTC   To get the local time of an Unspecified DateTime object  you therefore just need to do this   convertedDate ToLocalTime      The step of changing the Kind of the DateTime from Unspecified to UTC is unnecessary  Unspecified is assumed to be UTC for the purposes of ToLocalTime  http   msdn microsoft com en-us library system datetime tolocaltime aspx

User · Answer

I had the problem with it being in a data set being pushed across the wire  webservice to client  that it would automatically change because the DataColumn s DateType field was set to local  Make sure you check what the DateType is if your pushing DataSets across   If you don t want it to change  set it to Unspecified

User · Answer

I d just like to add a general note of caution   If all you are doing is getting the current time from the computer s internal clock to put a date time on the display or a report  then all is well   But if you are saving the date time information for later reference or are computing date times  beware   Let s say you determine that a cruise ship arrived in Honolulu on 20 Dec 2007 at 15 00 UTC   And you want to know what local time that was  1  There are probably at least three  locals  involved   Local may mean Honolulu  or it may mean where your computer is located  or it may mean the location where your customer is located  2  If you use the built-in functions to do the conversion  it will probably be wrong   This is because daylight savings time is  probably  currently in effect on your computer  but was NOT in effect in December   But Windows does not know this    all it has is one flag to determine if daylight savings time is currently in effect   And if it is currently in effect  then it will happily add an hour even to a date in December  3  Daylight savings time is implemented differently  or not at all  in various political subdivisions   Don t think that just because your country changes on a specific date  that other countries will too

User · Answer

I had the problem with it being in a data set being pushed across the wire  webservice to client  that it would automatically change because the DataColumn s DateType field was set to local  Make sure you check what the DateType is if your pushing DataSets across   If you don t want it to change  set it to Unspecified

User · Answer

I had the problem with it being in a data set being pushed across the wire  webservice to client  that it would automatically change because the DataColumn s DateType field was set to local  Make sure you check what the DateType is if your pushing DataSets across   If you don t want it to change  set it to Unspecified

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TimeZone CurrentTimeZone ToLocalTime date

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TimeZone CurrentTimeZone ToLocalTime date

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In answer to Dana s suggestion   The code sample now looks like   string date    Web service date   ToString  R   ci   DateTime convertedDate   DateTime Parse date               DateTime dt   TimeZone CurrentTimeZone ToLocalTime convertedDate     The original date was 20 08 08  the kind was UTC   Both  convertedDate  and  dt  are the same   21 08 08 10 00 26  the kind was local

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TimeZoneInfo ConvertTimeFromUtc timeUtc  TimeZoneInfo Local

User · Answer

In answer to Dana s suggestion   The code sample now looks like   string date    Web service date   ToString  R   ci   DateTime convertedDate   DateTime Parse date               DateTime dt   TimeZone CurrentTimeZone ToLocalTime convertedDate     The original date was 20 08 08  the kind was UTC   Both  convertedDate  and  dt  are the same   21 08 08 10 00 26  the kind was local

User · Answer

In answer to Dana s suggestion   The code sample now looks like   string date    Web service date   ToString  R   ci   DateTime convertedDate   DateTime Parse date               DateTime dt   TimeZone CurrentTimeZone ToLocalTime convertedDate     The original date was 20 08 08  the kind was UTC   Both  convertedDate  and  dt  are the same   21 08 08 10 00 26  the kind was local

User · Answer

This code block uses universal time to convert current DateTime object then converts it back to local DateTime  Works perfect for me I hope it helps  CreatedDate ToUniversalTime   ToLocalTime

User · Answer

I d look into using the System TimeZoneInfo class if you are in  NET 3 5  See http   msdn microsoft com en-us library system timezoneinfo aspx  This should take into account the daylight savings changes correctly      Coordinated Universal Time string from     DateTime Now ToUniversalTime   ToString  u    string date    2009-02-25 16 13 00Z       Local  NET timeZone  DateTime localDateTime   DateTime Parse date    DateTime utcDateTime   localDateTime ToUniversalTime        ID from       HKEY LOCAL MACHINE Software Microsoft Windows NT CurrentVersion Time Zone     See http   msdn microsoft com en-us library system timezoneinfo id aspx string nzTimeZoneKey    New Zealand Standard Time   TimeZoneInfo nzTimeZone   TimeZoneInfo FindSystemTimeZoneById nzTimeZoneKey   DateTime nzDateTime   TimeZoneInfo ConvertTimeFromUtc utcDateTime  nzTimeZone

User · Answer

I d just like to add a general note of caution   If all you are doing is getting the current time from the computer s internal clock to put a date time on the display or a report  then all is well   But if you are saving the date time information for later reference or are computing date times  beware   Let s say you determine that a cruise ship arrived in Honolulu on 20 Dec 2007 at 15 00 UTC   And you want to know what local time that was  1  There are probably at least three  locals  involved   Local may mean Honolulu  or it may mean where your computer is located  or it may mean the location where your customer is located  2  If you use the built-in functions to do the conversion  it will probably be wrong   This is because daylight savings time is  probably  currently in effect on your computer  but was NOT in effect in December   But Windows does not know this    all it has is one flag to determine if daylight savings time is currently in effect   And if it is currently in effect  then it will happily add an hour even to a date in December  3  Daylight savings time is implemented differently  or not at all  in various political subdivisions   Don t think that just because your country changes on a specific date  that other countries will too

User · Answer

I d look into using the System TimeZoneInfo class if you are in  NET 3 5  See http   msdn microsoft com en-us library system timezoneinfo aspx  This should take into account the daylight savings changes correctly      Coordinated Universal Time string from     DateTime Now ToUniversalTime   ToString  u    string date    2009-02-25 16 13 00Z       Local  NET timeZone  DateTime localDateTime   DateTime Parse date    DateTime utcDateTime   localDateTime ToUniversalTime        ID from       HKEY LOCAL MACHINE Software Microsoft Windows NT CurrentVersion Time Zone     See http   msdn microsoft com en-us library system timezoneinfo id aspx string nzTimeZoneKey    New Zealand Standard Time   TimeZoneInfo nzTimeZone   TimeZoneInfo FindSystemTimeZoneById nzTimeZoneKey   DateTime nzDateTime   TimeZoneInfo ConvertTimeFromUtc utcDateTime  nzTimeZone

User · Answer

TimeZoneInfo ConvertTimeFromUtc timeUtc  TimeZoneInfo Local

User · Answer

Don t forget if you already have a DateTime object and are not sure if it s UTC or Local  it s easy enough to use the methods on the object directly   DateTime convertedDate   DateTime Parse date   DateTime localDate   convertedDate ToLocalTime         How do we adjust for the extra hour    Unless specified  net will use the local pc settings  I d have a read of  http   msdn microsoft com en-us library system globalization daylighttime aspx  By the looks the code might look something like   DaylightTime daylight   TimeZone CurrentTimeZone GetDaylightChanges  year      And as mentioned above double check what timezone setting your server is on  There are articles on the net for how to safely affect the changes in IIS

User · Answer

I know this is an older question  but I ran into a similar situation  and I wanted to share what I had found for future searchers  possibly including myself      DateTime Parse   can be tricky -- see here for example   If the DateTime is coming from a Web service or some other source with a known format  you might want to consider something like    DateTime ParseExact dateString                       MM dd yyyy HH mm ss                       CultureInfo InvariantCulture                      DateTimeStyles AssumeUniversal   DateTimeStyles AdjustToUniversal    or  even better   DateTime TryParseExact        The AssumeUniversal flag tells the parser that the date time is already UTC  the combination of AssumeUniversal and AdjustToUniversal tells it not to convert the result to  local  time  which it will try to do by default    I personally try to deal exclusively with UTC in the business   application   service layer s  anyway   But bypassing the conversion to local time also speeds things up -- by 50  or more in my tests  see below    Here s what we were doing before     DateTime Parse dateString  new CultureInfo  en-US      We had profiled the app and found that the DateTime Parse represented a significant percentage of CPU usage    Incidentally  the CultureInfo constructor was not a significant contributor to CPU usage      So I set up a console app to parse a date time string 10000 times in a variety of ways   Bottom line  Parse   10 sec ParseExact    converting to local  20-45 ms ParseExact    not converting to local  10-15 ms     and yes  the results for Parse   are in seconds  whereas the others are in milliseconds

User · Answer

For strings such as 2012-09-19 01 27 30 000  DateTime Parse cannot tell what time zone the date and time are from   DateTime has a Kind property  which can have one of three time zone options    Unspecified Local Utc   NOTE If you are wishing to represent a date time other than UTC or your local time zone  then you should use DateTimeOffset     So for the code in your question   DateTime convertedDate   DateTime Parse dateStr    var kind   convertedDate Kind     will equal DateTimeKind Unspecified   You say you know what kind it is  so tell it   DateTime convertedDate   DateTime SpecifyKind      DateTime Parse dateStr       DateTimeKind Utc    var kind   convertedDate Kind     will equal DateTimeKind Utc   Now  once the system knows its in UTC time  you can just call ToLocalTime   DateTime dt   convertedDate ToLocalTime      This will give you the result you require

User · Answer

Don t forget if you already have a DateTime object and are not sure if it s UTC or Local  it s easy enough to use the methods on the object directly   DateTime convertedDate   DateTime Parse date   DateTime localDate   convertedDate ToLocalTime         How do we adjust for the extra hour    Unless specified  net will use the local pc settings  I d have a read of  http   msdn microsoft com en-us library system globalization daylighttime aspx  By the looks the code might look something like   DaylightTime daylight   TimeZone CurrentTimeZone GetDaylightChanges  year      And as mentioned above double check what timezone setting your server is on  There are articles on the net for how to safely affect the changes in IIS

User · Answer

TimeZone CurrentTimeZone ToLocalTime date

User · Answer

I had the problem with it being in a data set being pushed across the wire  webservice to client  that it would automatically change because the DataColumn s DateType field was set to local  Make sure you check what the DateType is if your pushing DataSets across   If you don t want it to change  set it to Unspecified

User · Answer

I d just like to add a general note of caution   If all you are doing is getting the current time from the computer s internal clock to put a date time on the display or a report  then all is well   But if you are saving the date time information for later reference or are computing date times  beware   Let s say you determine that a cruise ship arrived in Honolulu on 20 Dec 2007 at 15 00 UTC   And you want to know what local time that was  1  There are probably at least three  locals  involved   Local may mean Honolulu  or it may mean where your computer is located  or it may mean the location where your customer is located  2  If you use the built-in functions to do the conversion  it will probably be wrong   This is because daylight savings time is  probably  currently in effect on your computer  but was NOT in effect in December   But Windows does not know this    all it has is one flag to determine if daylight savings time is currently in effect   And if it is currently in effect  then it will happily add an hour even to a date in December  3  Daylight savings time is implemented differently  or not at all  in various political subdivisions   Don t think that just because your country changes on a specific date  that other countries will too

User · Answer

TimeZone CurrentTimeZone ToLocalTime date

User · Answer

I came across this question as I was having a problem with the UTC dates you get back through the twitter API (created_at field on a status); I need to convert them to DateTime. None of the answers/ code samples in the answers on this page were sufficient to stop me getting a "String was not recognized as a valid DateTime" error (but it's the closest I have got to finding the correct answer on SO)

Posting this link here in case this helps someone else - the answer I needed was found on this blog post: http://www.wduffy.co.uk/blog/parsing-dates-when-aspnets-datetimeparse-doesnt-work/ - basically use DateTime.ParseExact with a format string instead of DateTime.Parse

User · Answer

I d look into using the System TimeZoneInfo class if you are in  NET 3 5  See http   msdn microsoft com en-us library system timezoneinfo aspx  This should take into account the daylight savings changes correctly      Coordinated Universal Time string from     DateTime Now ToUniversalTime   ToString  u    string date    2009-02-25 16 13 00Z       Local  NET timeZone  DateTime localDateTime   DateTime Parse date    DateTime utcDateTime   localDateTime ToUniversalTime        ID from       HKEY LOCAL MACHINE Software Microsoft Windows NT CurrentVersion Time Zone     See http   msdn microsoft com en-us library system timezoneinfo id aspx string nzTimeZoneKey    New Zealand Standard Time   TimeZoneInfo nzTimeZone   TimeZoneInfo FindSystemTimeZoneById nzTimeZoneKey   DateTime nzDateTime   TimeZoneInfo ConvertTimeFromUtc utcDateTime  nzTimeZone

User · Answer

I d just like to add a general note of caution   If all you are doing is getting the current time from the computer s internal clock to put a date time on the display or a report  then all is well   But if you are saving the date time information for later reference or are computing date times  beware   Let s say you determine that a cruise ship arrived in Honolulu on 20 Dec 2007 at 15 00 UTC   And you want to know what local time that was  1  There are probably at least three  locals  involved   Local may mean Honolulu  or it may mean where your computer is located  or it may mean the location where your customer is located  2  If you use the built-in functions to do the conversion  it will probably be wrong   This is because daylight savings time is  probably  currently in effect on your computer  but was NOT in effect in December   But Windows does not know this    all it has is one flag to determine if daylight savings time is currently in effect   And if it is currently in effect  then it will happily add an hour even to a date in December  3  Daylight savings time is implemented differently  or not at all  in various political subdivisions   Don t think that just because your country changes on a specific date  that other countries will too

User · Answer

In answer to Dana s suggestion   The code sample now looks like   string date    Web service date   ToString  R   ci   DateTime convertedDate   DateTime Parse date               DateTime dt   TimeZone CurrentTimeZone ToLocalTime convertedDate     The original date was 20 08 08  the kind was UTC   Both  convertedDate  and  dt  are the same   21 08 08 10 00 26  the kind was local

User · Answer

This code block uses universal time to convert current DateTime object then converts it back to local DateTime  Works perfect for me I hope it helps  CreatedDate ToUniversalTime   ToLocalTime

User · Answer

Don t forget if you already have a DateTime object and are not sure if it s UTC or Local  it s easy enough to use the methods on the object directly   DateTime convertedDate   DateTime Parse date   DateTime localDate   convertedDate ToLocalTime         How do we adjust for the extra hour    Unless specified  net will use the local pc settings  I d have a read of  http   msdn microsoft com en-us library system globalization daylighttime aspx  By the looks the code might look something like   DaylightTime daylight   TimeZone CurrentTimeZone GetDaylightChanges  year      And as mentioned above double check what timezone setting your server is on  There are articles on the net for how to safely affect the changes in IIS

User · Answer

I know this is an older question  but I ran into a similar situation  and I wanted to share what I had found for future searchers  possibly including myself      DateTime Parse   can be tricky -- see here for example   If the DateTime is coming from a Web service or some other source with a known format  you might want to consider something like    DateTime ParseExact dateString                       MM dd yyyy HH mm ss                       CultureInfo InvariantCulture                      DateTimeStyles AssumeUniversal   DateTimeStyles AdjustToUniversal    or  even better   DateTime TryParseExact        The AssumeUniversal flag tells the parser that the date time is already UTC  the combination of AssumeUniversal and AdjustToUniversal tells it not to convert the result to  local  time  which it will try to do by default    I personally try to deal exclusively with UTC in the business   application   service layer s  anyway   But bypassing the conversion to local time also speeds things up -- by 50  or more in my tests  see below    Here s what we were doing before     DateTime Parse dateString  new CultureInfo  en-US      We had profiled the app and found that the DateTime Parse represented a significant percentage of CPU usage    Incidentally  the CultureInfo constructor was not a significant contributor to CPU usage      So I set up a console app to parse a date time string 10000 times in a variety of ways   Bottom line  Parse   10 sec ParseExact    converting to local  20-45 ms ParseExact    not converting to local  10-15 ms     and yes  the results for Parse   are in seconds  whereas the others are in milliseconds

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