Wednesday, 15 July 2009

Gotcha: UTC vs Local TimeZones with ActiveResource

So... your database is filled with datetime data and it's all configured to localtime, not UTC... We also have this you-beat nifty ability to set all our datetime-handling functionality to a given timezone by setting, say: config.time_zone = 'London' in config/environments.rb... or do we?

If you also use ActiveResource (or the new, actually-working HyperactiveResource), you'll find that suddenly you're getting a UTC-local timezone issue once more.

The problem is that the xml that comes back from a remote API is converted into a Date/DateTime using the core-extension to the Hash.from_xml method... which has the following LOC:

"datetime"     =>  { |time|    ::Time.parse(time).utc rescue ::DateTime.parse(time).utc }

The fix

You need to do two things. Firstly. Hack that line[1] and replace it with:

"datetime"     =>  { |time| rescue },

Secondly... somehow it doesn't pick up the timezone even though it's been helpfully added in via the config... so you need to open up config/environments.rb (or create a rails initializer) and put: = 'London'[2]
in there (outside the rails initialization block).

[1]To hack rails, you can either
a) hack on your own rails gem = risky... will be overwritten the next time you sudo gem update or
b) rake rails:freeze:edge - which means you have your rails in your own vendor/rails directory... but means you have to rake rails:update manually... up to you which you hate more.

[2]Obviously substituting your own timeZone as appropriate here. See the TimeZone doc for what you can pass in.

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