Rails: How to parse date-time string into a specific time zone

I'm using Rails 3.2 and ruby 1.9.3 on Debian. I have an app that collects a date, time, and timezone in the form of strings via an HTML form. Something like this:

start_date: "04-15-2010",
start_time: "10:00:00",
timezone: "Central Time (US & Canada)"

What I'd like to do is parse these 3 elements into a single date that is saved into my database as UTC, which in this case would add 7 hours to the start time, once it's in the UTC time zone. So the stored time would be 17:00 once it's in the DB as UTC instead of the received Central time.

I have tried something like this to parse the date:

ActiveSupport::TimeZone[timezone].at DateTime.strptime("{ 2012-04-09 20:00:00 }", "{ %Y-%m-%d %H:%M:%S }").to_i

However, I'm not able to incorporate the time zone into the resulting time with %Z. It either doesn't parse or the time is interpreted as UTC not Central time. So my question is, how to coerce a date string into a certain time zone without changing the value of the actual date/time stored. I'd like to be able to parse the string into a date/time object that includes the correct time zone with it at that time so that future time zone conversions are accurate. I've looked all over and can't find a way to do this. It's strange, since this seems like something common one does with dates inputted from HTML forms. Thank you for any help.

Solution 1:

Try this:

zone = "Central Time (US & Canada)"  

ActiveSupport::TimeZone[zone].parse("2013-04-03 17:47:00")

Solution 2:

Use String#in_time_zone (Rails 4+)

I personally prefer using String#in_time_zone:

>> '22.09.1986 10:30'.in_time_zone('Central Time (US & Canada)')
# => Mon, 22 Sep 1986 10:30:00 CDT -05:00

This parses the date and time in the String into the time zone provided.