Which should I always parse date times with? DateTime, Time, Time.zone?

Question

In Rails, I see I have a few options to parse a date and a date-time. What is the best practice for parsing dates for the sole purpose of persisting them into the DB via ActiveRecord? And why?

Time.zone.parse(...)
Time.parse(...)
DateTime.parse(...)

Answer 1

Go with Time.zone.parse if you just want to write into ActiveRecord.

DateTime should be avoided. If you're handling dates, you should use Date.parse instead.

Beyond that, it depends on whether the input comes with timezone information, what the current timezone is set to, and whether you want timezones in your data.

Time.zone.parse will return an ActiveSupport::TimeWithZone, defaulting to UTC.

> Time.zone.parse("12:30")
=> Thu, 10 May 2012 12:30:00 UTC +00:00 

Time.parse will return a Time, with a zone if it's specified in the input, or the local TZ.

> Time.parse("12:30")
=> 2012-05-09 12:30:00 -0700 

For a more detailed explanation of Ruby time comparisons and precision, read this blog post:

http://blog.solanolabs.com/rails-time-comparisons-devil-details-etc/