Ruby - Date & Time

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 be unable on your system to represent dates before 1970 or after 2038.
This chapter makes you familiar with all the most wanted concepts of date and time.
Following is the simple example to get current date and time −
#!/usr/bin/ruby -w

time1 = Time.new
puts "Current Time : " + time1.inspect

# Time.now is a synonym:
time2 = Time.now
puts "Current Time : " + time2.inspect
This will produce the following result −
Current Time : Mon Jun 02 12:02:39 -0700 2008
Current Time : Mon Jun 02 12:02:39 -0700 2008

We can use Time object to get various components of date and time. Following is the example showing the same −
#!/usr/bin/ruby -w

time = Time.new

# Components of a Time
puts "Current Time : " + time.inspect
puts time.year    # => Year of the date 
puts time.month   # => Month of the date (1 to 12)
puts time.day     # => Day of the date (1 to 31 )
puts time.wday    # => 0: Day of week: 0 is Sunday
puts time.yday    # => 365: Day of year
puts time.hour    # => 23: 24-hour clock
puts time.min     # => 59
puts time.sec     # => 59
puts time.usec    # => 999999: microseconds
puts time.zone    # => "UTC": timezone name
This will produce the following result −
Current Time : Mon Jun 02 12:03:08 -0700 2008
2008
6
2
1
154
12
3
8
247476
UTC

These two functions can be used to format date in a 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 the components in an array in the following format −
[sec,min,hour,day,month,year,wday,yday,isdst,zone]

Try the following −
#!/usr/bin/ruby -w

time = Time.new
values = time.to_a
p values
This will generate the 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 −
#!/usr/bin/ruby -w

time = Time.new
values = time.to_a
puts Time.utc(*values)
This will generate the 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
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
There are various ways to format date and time. Here is one example showing a few −
#!/usr/bin/ruby -w

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 the 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

These directives in the following table are used with the method Time.strftime.
%a
The abbreviated weekday name (Sun).
%A
The full weekday name (Sunday).
%b
The abbreviated month name (Jan).
%B
The full month name (January).
%c
The preferred local date and time representation.
%d
Day of the month (01 to 31).
%H
Hour of the day, 24-hour clock (00 to 23).
%I
Hour of the day, 12-hour clock (01 to 12).
%j
Day of the year (001 to 366).
%m
Month of the year (01 to 12).
%M
Minute of the hour (00 to 59).
%p
Meridian indicator (AM or PM).
%S
Second of the minute (00 to 60).
%U
Week number of the current year, starting with the first Sunday as the first day of the first week (00 to 53).
%W
Week number of the current year, starting with the first Monday as the first day of the first week (00 to 53).
%w
Day of the week (Sunday is 0, 0 to 6).
%x
Preferred representation for the date alone, no time.
%X
Preferred representation for the time alone, no date.
%y
Year without a century (00 to 99).
%Y
Year with century.
%Z
Time zone name.
%%
Literal % character.
You can perform simple arithmetic with time as follows −
now = Time.now          # Current time
puts now

past = now - 10         # 10 seconds ago. Time - number => Time
puts past

future = now + 10  # 10 seconds from now Time + number => Time
puts future

diff = future - past     # => 10  Time - Time => number of seconds
puts diff
This will produce the following result −
Thu Aug 01 20:57:05 -0700 2013
Thu Aug 01 20:56:55 -0700 2013
Thu Aug 01 20:57:15 -0700 2013
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