[ruby-on-rails] Ruby/Rails: converting a Date to a UNIX timestamp

How would I get a UNIX timestamp (number of seconds since 1970 GMT) from a Date object in a Rails app?

I know Time#to_i returns a timestamp, but doing Date#to_time and then getting the timestamp results in something that's off by about a month (not sure why...).

Any help is appreciated, thanks!

Edit: OK, I think I figured it out- I was processing a date several times in a loop, and each time the date was moved a little because of a time zone mismatch, ultimately leading to my timestamp being a month off. Still, I'd be interested in knowing if there's any way to do this without relying on Date#to_time.

I get the following when I try it:

>> Date.today.to_time.to_i
=> 1259244000
>> Time.now.to_i
=> 1259275709

The difference between these two numbers is due to the fact that Date does not store the hours, minutes or seconds of the current time. Converting a Date to a Time will result in that day, midnight.

DateTime.new(2012, 1, 15).to_time.to_i

The suggested options of using to_utc or utc to fix the local time offset does not work. For me I found using Time.utc() worked correctly and the code involves less steps:

> Time.utc(2016, 12, 25).to_i
=> 1482624000 # correct

vs

> Date.new(2016, 12, 25).to_time.utc.to_i
=> 1482584400 # incorrect

Here is what happens when you call utc after using Date....

> Date.new(2016, 12, 25).to_time
=> 2016-12-25 00:00:00 +1100 # This will use your system's time offset
> Date.new(2016, 12, 25).to_time.utc
=> 2016-12-24 13:00:00 UTC

...so clearly calling to_i is going to give the wrong timestamp.

Solution for Ruby 1.8 when you have an arbitrary DateTime object:

1.8.7-p374 :001 > require 'date'
 => true 
1.8.7-p374 :002 > DateTime.new(2012, 1, 15).strftime('%s')
 => "1326585600"