Ruby/Rails: converting a Date to a UNIX timestamp

Question

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.

score 391 · Accepted Answer · edited Jul 29 '22 at 18:18

391

The code date.to_time.to_i should work fine. The Rails console session below shows an example:

>> Date.new(2009,11,26).to_time
=> Thu Nov 26 00:00:00 -0800 2009
>> Date.new(2009,11,26).to_time.to_i
=> 1259222400
>> Time.at(1259222400)
=> Thu Nov 26 00:00:00 -0800 2009

Note that the intermediate DateTime object is in local time, so the timestamp might be several hours off from what you expect. If you want to work in UTC time, you can use DateTime's method "utc".

edited Jul 29 '22 at 18:18

Bruno Degomme

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answered Nov 26 '09 at 22:46

David Grayson

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DateTime doesn't have `to_utc` – Green Apr 21 '13 at 22:17
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`date.to_time.utc` is probably what he meant. – Adam Eberlin Apr 25 '13 at 08:50
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In Rails, through ActiveSupport, a DateTime instance does have a utc() method (also aliased to getutc) – Gokul Jun 28 '13 at 08:46

score 84 · Answer 2 · answered Nov 26 '09 at 22:49

84

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.

answered Nov 26 '09 at 22:49

Ryan Bigg

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... "will result in that day, midnight." __in the system time zone__ where it is ran, which makes it not very portable as this information is not included/implied by the value. Anyone who uses this solution to persist or expose the value, should probably convert it to UTC first. – Pelle Mar 07 '23 at 08:03

score 12 · Answer 3 · answered Nov 03 '13 at 15:13

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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"

answered Nov 03 '13 at 15:13

Nowaker

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score 10 · Answer 4 · answered Mar 11 '16 at 07:33

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.

score 4 · Answer 5 · answered Jan 18 '16 at 11:19

4

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

answered Jan 18 '16 at 11:19

wang sky

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Ruby/Rails: converting a Date to a UNIX timestamp

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