Difference between DateTime and Time in Ruby

Question

What\'s the difference between DateTime and Time classes in Ruby and what factors would cause me to choose one or the other?

Answer 1

I found such things like parsing and calculating the beginning/end of a day in different timezones are easier to do with DateTime, assuming you are using the ActiveSupport extensions.

In my case I needed to calculate the end of the day in a user's timezone (arbitrary) based on the user's local time which I received as a string, e.g. "2012-10-10 10:10 +0300"

With DateTime it's as simple as

irb(main):034:0> DateTime.parse('2012-10-10 10:10 +0300').end_of_day
=> Wed, 10 Oct 2012 23:59:59 +0300
# it preserved the timezone +0300

Now let's try it the same way with Time:

irb(main):035:0> Time.parse('2012-10-10 10:10 +0300').end_of_day
=> 2012-10-10 23:59:59 +0000
# the timezone got changed to the server's default UTC (+0000), 
# which is not what we want to see here.

Actually, Time needs to know the timezone before parsing (also note it's Time.zone.parse, not Time.parse):

irb(main):044:0> Time.zone = 'EET'
=> "EET"
irb(main):045:0> Time.zone.parse('2012-10-10 10:10 +0300').end_of_day
=> Wed, 10 Oct 2012 23:59:59 EEST +03:00

So, in this case it's definitely easier to go with DateTime.