how to find seconds since 1970 in java

Question

iam working with a real time project where i got a requirement to find seconds since 1970 january 1 I have used the following code to find out seconds but is giving wrong result The code is as follows   public long returnSeconds int year  int month  int date        Calendar calendar1   Calendar getInstance        Calendar calendar2   Calendar getInstance        calendar1 set 1970  01  01       calendar2 set year  month  date       long milliseconds1   calendar1 getTimeInMillis        long milliseconds2   calendar2 getTimeInMillis        long diff   milliseconds2 - milliseconds1      long seconds   diff   1000      return seconds      In the above in place of year month date I m passing 2011 10 1 and iam getting   1317510000   but the correct answer is   1317427200   Any help regarding this is very useful to me

User · Answer

Another option is to use the TimeUtils utility method  TimeUtils millisToUnit System currentTimeMillis    TimeUnit SECONDS

User · Answer

java time  Using the java time framework built into Java 8 and later   import java time LocalDate  import java time ZoneId   int year   2011  int month   10  int day   1  int date   LocalDate of year  month  day    date atStartOfDay ZoneId of  UTC    toEpochSecond    Long   1317427200

User · Answer

Since Java8   java time Instant now   getEpochSecond

User · Answer

The difference you see is most likely because you don t zero the hour  minute  second and milliseconds fields of your Calendar instances  Calendar getInstance   gives you the current date and time  just like new Date   or System currentTimeMillis     Note that the month field of Calendar is zero-based  i e  January is 0  not 1   Also  don t prefix numbers with zero  this might look nice and it even works till you reach 8  08 isn t a valid numeral in Java  Prefixing numerals with zero makes the compiler assume you re defining them as octal numerals which only works up to 07  for single digits    Just drop calendar1 completely  1970-01-01 00 00 00 000 is the begin of the epoch  i e  zero anyway  and do this   public long returnSeconds int year  int month  int date        final Calendar cal   Calendar getInstance        cal set year  month  date  0  0  0       cal set Calendar MILLISECOND  0       return cal getTimeInMillis     1000

User · Answer

The answer you want   1317427200   is achieved if your reference months are January and October  If so  the dates you are looking for are 1970-JAN-01 and 2011-OCT-01  correct   Then the problem are these numbers you are using for your months   See  if you check the Calendar API documentation or even the constants provided in there   Calendar JANUARY    Calendar FEBRUARY  and so on   you ll discover that months start at 0  being January     So checking your code  you are passing february and november  which would result in  1317510000     Best regards

User · Answer

It s Date getTime

User · Answer

Based on your desire that 1317427200 be the output  there are several layers of issue to address    First as others have mentioned  java already uses a UTC 1 1 1970 epoch   There is normally no need to calculate the epoch and perform subtraction unless you have weird locale rules  Second  when you create a new Calendar it s initialized to  now  so it includes the time of day   Changing the year month day doesn t affect the time of day fields   So if you want it to represent midnight of the date  you need to zero out the calendar before you set the date  Third  you haven t specified how you re supposed to handle time zones   Daylight Savings can cause differences in the absolute number of seconds represented by a particular calendar-on-the-wall-date  depending on where your JVM is running   Since epoch is in UTC  we probably want to work in UTC times   You may need to seek clarification from the makers of the system you re interfacing with  Fourth  months in Java are zero indexed   January is 0  October is 9    Putting all that together  Calendar calendar   Calendar getInstance TimeZone getTimeZone  UTC     calendar clear    calendar set 2011  Calendar OCTOBER  1   long secondsSinceEpoch   calendar getTimeInMillis     1000L    that will give you 1317427200

User · Answer

The methods Calendar getTimeInMillis   and Date getTime   both return milliseconds since 1 1 1970   For current time  you can use   long seconds   System currentTimeMillis     1000l

[java] how to find seconds since 1970 in java

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