Ruby Date & Time

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The Time class represents dates and times in Ruby. It is a thin layer over the system date and time functionality provided by the operating system. This class may have the same limitations as your operating system.

This tutorial will make you familiar with all the most wanted concepts of date and time.

Getting Current Date and Time:

Following is the simple example to get current date and time:

      time1 = Time.new
      
      puts "Current Time : #{time1.inspect}"
      
      # Time.now is a synonym:
      time2 = Time.now
      puts "Current Time : #{time2.inspect}"
      

This will produce following result:

      Current Time : Mon Jun 02 12:02:39 -0700 2008
      Current Time : Mon Jun 02 12:02:39 -0700 2008
      

 

Getting components of a Date & Time:

We can use Time object to get various components of date and time. Following is the example showing the same:

      ctime = Time.new
      puts "If current time is: #{ctime}"
      
      outputs = [ :year, :month, :day, :wday, :yday,
                  :hour, :min, :sec, :usec, :zone ]
      
      outputs.each do |method|
        puts "ctime.#{method} will produce #{ctime.send(method)}"
      end
      

This will produce following result:

      If current time is: Sat Jun 05 02:04:21 -0300 2010
      ctime.year will produce 2010
      ctime.month will produce 6
      ctime.day will produce 5
      ctime.wday will produce 6
      ctime.yday will produce 156
      ctime.hour will produce 2
      ctime.min will produce 4
      ctime.sec will produce 21
      ctime.usec will produce 140625
      ctime.zone will produce E. South America Standard Time
      

 

Time.utc, Time.gm and Time.local Functions:

These two functions can be used to format date in standard format as follows:

      # July 8, 2008
      Time.local(2008, 7, 8)  
      # July 8, 2008, 09:10am, local time
      Time.local(2008, 7, 8, 9, 10)   
      # July 8, 2008, 09:10 UTC
      Time.utc(2008, 7, 8, 9, 10)  
      # July 8, 2008, 09:10:11 GMT (same as UTC)
      Time.gm(2008, 7, 8, 9, 10, 11)
      

Following is the example to get all components in an array in the following format:

      [sec,min,hour,day,month,year,wday,yday,isdst,zone]
      

Try the following:

      time = Time.new
      
      values = time.to_a
      p values
      

This will generate following result:

      [26, 10, 12, 2, 6, 2008, 1, 154, false, "MST"]
      

This array could be passed to Time.utc or Time.local functions to get different format of dates as follows:

      time = Time.new
      
      values = time.to_a
      puts Time.utc(*values)
      

This will generate following result:

      Mon Jun 02 12:15:36 UTC 2008
      

Following is the way to get time represented internally as seconds since the (platform-dependent) epoch:

      # Returns number of seconds since epoch
      time = Time.now.to_i  
      
      # Convert number of seconds into Time object.
      Time.at(time)
      
      # Returns second since epoch which includes microseconds
      time = Time.now.to_f
      

 

Timezones and daylight savings time:

You can use a Time object to get all the information related to Timezones and daylight savings as follows:

      time = Time.new
      
      # Here is the interpretation
      time.zone       # => "UTC": return the timezone
      time.utc_offset # => 0: UTC is 0 seconds offset from UTC
      time.zone       # => "PST" (or whatever your timezone is)
      time.isdst      # => false: If UTC does not have DST.
      time.utc?       # => true: if t is in UTC time zone
      time.localtime  # Convert to local timezone.
      time.gmtime     # Convert back to UTC.
      time.getlocal   # Return a new Time object in local zone
      time.getutc     # Return a new Time object in UTC
      

 

Formatting Times and Dates:

There are various ways to format date and time. Here is one example showing a few:

      time = Time.new
      
      puts time.to_s
      puts time.ctime
      puts time.localtime
      puts time.strftime("%Y-%m-%d %H:%M:%S")
      

This will produce following result:

      Mon Jun 02 12:35:19 -0700 2008
      Mon Jun  2 12:35:19 2008
      Mon Jun 02 12:35:19 -0700 2008
      2008-06-02 12:35:19
      

 

Time arithmetic:

You can do simple arithmetic with time as follows:

      now = Time.now     # Current time
      past = now - 10    # 10 seconds ago. Time - number => Time
      future = now + 10  # 10 seconds from now Time + number => Time
      future - now       # => 10  Time - Time => number of seconds
      

 

Date and DateTime classes:

There are many Date and Time operations that could be performed using these classes:

      date = Date.new(2008, 12, 22)
      puts date
      
      dtime = DateTime.new(2009, 7, 16, 14, 30)
      puts dtime
      
      # Convert a UTC offset measured in minutes to one measured in a
      # fraction of a day.
      offset = Rational(-14453, 60 * 60 * 24)
      today = DateTime.new(2010, 6, 5, 02, 26, 40, offset)
      puts today
      
      birthday = Date.new(2010, 11, 23)
      puts birthday
      
      time_until = birthday - today
      hours,minutes,seconds,frac = Date.day_fraction_to_time(time_until)
      
      puts "My birthday will be in:"
      puts "#{hours} hours, #{minutes} minutes and #{seconds} seconds."
      

This will produce following result:

      2008-12-22
      2009-07-16T14:30:00+00:00
      2010-06-05T02:26:40-04:00
      2010-11-23
      My birthday will be in:
      4097 hours, 32 minutes and 27 seconds.