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.

Getting Current 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

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

#!/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

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

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

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 −

#!/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

Time Formatting Directives

These directives in the following table are used with the method Time.strftime.

Sr.No.	Directive & Description
1	%aThe abbreviated weekday name (Sun).
2	%AThe full weekday name (Sunday).
3	%bThe abbreviated month name (Jan).
4	%BThe full month name (January).
5	%cThe preferred local date and time representation.
6	%dDay of the month (01 to 31).
7	%HHour of the day, 24-hour clock (00 to 23).
8	%IHour of the day, 12-hour clock (01 to 12).
9	%jDay of the year (001 to 366).
10	%mMonth of the year (01 to 12).
11	%MMinute of the hour (00 to 59).
12	%pMeridian indicator (AM or PM).
13	%SSecond of the minute (00 to 60).
14	%UWeek number of the current year, starting with the first Sunday as the first day of the first week (00 to 53).
15	%WWeek number of the current year, starting with the first Monday as the first day of the first week (00 to 53).
16	%wDay of the week (Sunday is 0, 0 to 6).
17	%xPreferred representation for the date alone, no time.
18	%XPreferred representation for the time alone, no date.
19	%yYear without a century (00 to 99).
20	%YYear with century.
21	%ZTime zone name.
22	%%Literal % character.

Time Arithmetic

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
20.0