Define "current time" when starting Rails? - ruby-on-rails

Question

I have an app that changes behavior based on the time of the day, and I'd like to be able to just spin up the server and test how it works at different times.
Ideally, I'd like to be able to just pass in the time as an argument when I run rails s, like rails s TIME=2014-02-26 22:06:11 -0500.

Answer 1

In config/locales/application.rb you can set the timezone before running rails s.
config.time_zone = 'Alaska'
If you're running OS X, you can also set the system time in the terminal before running rails s.
date 022611002013
The format is [month][day][hh][mm][year], so the above is 11:00 February 26, 2013. You can change your system time back to the current time in the terminal or Date and Time preferences panel.

Answer 2

You can actually read environment variables from within rails (actually Ruby). This is how to do it:
require 'date'
$startup_time = DateTime.parse(ENV['STARTUP_TIME']) rescue DateTime.now
puts "Server started at: #{$startup_time}"
You'd call this code placed in pull_time.rb like this:
STARTUP_TIME="2014-02-26 22:06:11 -0500" ruby pull_time.rb
In order to have this global variable work in Rails, you want to add it to an initializer.
So put the code above in config/initializers/set_startup_time.rb
You can now access $startup_time anywhere in your code. Just pass STARTUP_TIME as an environment variable to rails.
STARTUP_TIME=2014-02-26 22:06:11 -0500 rails s

Answer 3

Rails server uses time of the hosting machine. So if you are running on local machine then changing the time of the local operating system will also have effect on your rails server
If it's hosted on another server then you have to change that server's time.

Answer 4

Don't try changing the time of your server. That can play real havoc with cron jobs or other time-based services.
Instead, have you tried defining the starting time as a specific value in your code then running the server? Then set it to the next time you need, and run the server again?
Time.new(2013, 12, 31, 12, 59, 59) # => 2013-12-31 12:59:59 -0700
You could also use the time as an integer, using the number of seconds that represent the time you want the server to think it is. Pass that in as an ENV hash element, then check to see if it's defined. If it is, define the time based on that value, otherwise don't define the ENV value and the server will run as normal:
ENV['SERVER_TIME'] = '1388519999'
server_time = ENV['SERVER_TIME'] ? Time.at(ENV['SERVER_TIME'].to_i) : Time.now
server_time # => 2013-12-31 12:59:59 -0700
Then, when you need to test the server, you could write a little shell script that sets that value and runs rails s, test the server then quit it, and rerun the shell script with a different value.

Answer 5

You can change Rails' internal timezone by adding config.time_zone = 'Pacific' to application.rb.
If you're deploying to Heroku, you can do the same slightly differently: heroku config:add TZ="Europe/Athens".
However, the downside is that neither of these commands allows you to define a specific time for the app (just the timezone, so you get the current time in another timezone), nor can you run these from command-line when starting your local Rails server.

Answer 6

Rails server determine time from the hosting machine
So changing the system's time would do the trick
EDIT:
As 'sevenseacat' said in comment
you can also use gem timecop to test your application without changing system's time.