timev.rb: moved class rdoc from time.c

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+# Time is an abstraction of dates and times. Time is stored internally as
+# the number of seconds with subsecond since the _Epoch_,
+# 1970-01-01 00:00:00 UTC.
+#
+# The Time class treats GMT
+# (Greenwich Mean Time) and UTC (Coordinated Universal Time) as equivalent.
+# GMT is the older way of referring to these baseline times but persists in
+# the names of calls on POSIX systems.
+#
+# Note: A \Time object uses the resolution available on your system clock.
+#
+# All times may have subsecond. Be aware of this fact when comparing times
+# with each other -- times that are apparently equal when displayed may be
+# different when compared.
+# (Since Ruby 2.7.0, Time#inspect shows subsecond but
+# Time#to_s still doesn't show subsecond.)
+#
+# == Examples
+#
+# All of these examples were done using the EST timezone which is GMT-5.
+#
+# === Creating a New \Time Instance
+#
+# You can create a new instance of Time with Time.new. This will use the
+# current system time. Time.now is an alias for this. You can also
+# pass parts of the time to Time.new such as year, month, minute, etc. When
+# you want to construct a time this way you must pass at least a year. If you
+# pass the year with nothing else time will default to January 1 of that year
+# at 00:00:00 with the current system timezone. Here are some examples:
+#
+#   Time.new(2002)         #=> 2002-01-01 00:00:00 -0500
+#   Time.new(2002, 10)     #=> 2002-10-01 00:00:00 -0500
+#   Time.new(2002, 10, 31) #=> 2002-10-31 00:00:00 -0500
+#
+# You can pass a UTC offset:
+#
+#   Time.new(2002, 10, 31, 2, 2, 2, "+02:00") #=> 2002-10-31 02:02:02 +0200
+#
+# Or a timezone object:
+#
+#   zone = timezone("Europe/Athens")      # Eastern European Time, UTC+2
+#   Time.new(2002, 10, 31, 2, 2, 2, zone) #=> 2002-10-31 02:02:02 +0200
+#
+# You can also use Time.local and Time.utc to infer
+# local and UTC timezones instead of using the current system
+# setting.
+#
+# You can also create a new time using Time.at which takes the number of
+# seconds (with subsecond) since the {Unix
+# Epoch}[https://en.wikipedia.org/wiki/Unix_time].
+#
+#   Time.at(628232400) #=> 1989-11-28 00:00:00 -0500
+#
+# === Working with an Instance of \Time
+#
+# Once you have an instance of Time there is a multitude of things you can
+# do with it. Below are some examples. For all of the following examples, we
+# will work on the assumption that you have done the following:
+#
+#   t = Time.new(1993, 02, 24, 12, 0, 0, "+09:00")
+#
+# Was that a monday?
+#
+#   t.monday? #=> false
+#
+# What year was that again?
+#
+#   t.year #=> 1993
+#
+# Was it daylight savings at the time?
+#
+#   t.dst? #=> false
+#
+# What's the day a year later?
+#
+#   t + (60*60*24*365) #=> 1994-02-24 12:00:00 +0900
+#
+# How many seconds was that since the Unix Epoch?
+#
+#   t.to_i #=> 730522800
+#
+# You can also do standard functions like compare two times.
+#
+#   t1 = Time.new(2010)
+#   t2 = Time.new(2011)
+#
+#   t1 == t2 #=> false
+#   t1 == t1 #=> true
+#   t1 <  t2 #=> true
+#   t1 >  t2 #=> false
+#
+#   Time.new(2010,10,31).between?(t1, t2) #=> true
+#
+# == What's Here
+#
+# \Class \Time provides methods that are useful for:
+#
+# - {Creating \Time objects}[#class-Time-label-Methods+for+Creating].
+# - {Fetching \Time values}[#class-Time-label-Methods+for+Fetching].
+# - {Querying a \Time object}[#class-Time-label-Methods+for+Querying].
+# - {Comparing \Time objects}[#class-Time-label-Methods+for+Comparing].
+# - {Converting a \Time object}[#class-Time-label-Methods+for+Converting].
+# - {Rounding a \Time}[#class-Time-label-Methods+for+Rounding].
+#
+# === Methods for Creating
+#
+# - ::new: Returns a new time from specified arguments (year, month, etc.),
+#   including an optional timezone value.
+# - ::local (aliased as ::mktime): Same as ::new, except the
+#   timezone is the local timezone.
+# - ::utc (aliased as ::gm): Same as ::new, except the timezone is UTC.
+# - ::at: Returns a new time based on seconds since epoch.
+# - ::now: Returns a new time based on the current system time.
+# - #+ (plus): Returns a new time increased by the given number of seconds.
+# - {-}[#method-i-2D] (minus): Returns a new time
+#                              decreased by the given number of seconds.
+#
+# === Methods for Fetching
+#
+# - #year: Returns the year of the time.
+# - #month (aliased as #mon): Returns the month of the time.
+# - #mday (aliased as #day): Returns the day of the month.
+# - #hour: Returns the hours value for the time.
+# - #min: Returns the minutes value for the time.
+# - #sec: Returns the seconds value for the time.
+# - #usec (aliased as #tv_usec): Returns the number of microseconds
+#   in the subseconds value of the time.
+# - #nsec (aliased as #tv_nsec: Returns the number of nanoseconds
+#   in the subsecond part of the time.
+# - #subsec: Returns the subseconds value for the time.
+# - #wday: Returns the integer weekday value of the time (0 == Sunday).
+# - #yday: Returns the integer yearday value of the time (1 == January 1).
+# - #hash: Returns the integer hash value for the time.
+# - #utc_offset (aliased as #gmt_offset and #gmtoff): Returns the offset
+#   in seconds between time and UTC.
+# - #to_f: Returns the float number of seconds since epoch for the time.
+# - #to_i (aliased as #tv_sec): Returns the integer number of seconds since epoch
+#   for the time.
+# - #to_r: Returns the Rational number of seconds since epoch for the time.
+# - #zone: Returns a string representation of the timezone of the time.
+#
+# === Methods for Querying
+#
+# - #utc? (aliased as #gmt?): Returns whether the time is UTC.
+# - #dst? (aliased as #isdst): Returns whether the time is DST (daylight saving time).
+# - #sunday?: Returns whether the time is a Sunday.
+# - #monday?: Returns whether the time is a Monday.
+# - #tuesday?: Returns whether the time is a Tuesday.
+# - #wednesday?: Returns whether the time is a Wednesday.
+# - #thursday?: Returns whether the time is a Thursday.
+# - #friday?: Returns whether time is a Friday.
+# - #saturday?: Returns whether the time is a Saturday.
+#
+# === Methods for Comparing
+#
+# - {#<=>}[#method-i-3C-3D-3E]: Compares +self+ to another time.
+# - #eql?: Returns whether the time is equal to another time.
+#
+# === Methods for Converting
+#
+# - #asctime (aliased as #ctime): Returns the time as a string.
+# - #inspect: Returns the time in detail as a string.
+# - #strftime: Returns the time as a string, according to a given format.
+# - #to_a: Returns a 10-element array of values from the time.
+# - #to_s: Returns a string representation of the time.
+# - #getutc (aliased as #getgm): Returns a new time converted to UTC.
+# - #getlocal: Returns a new time converted to local time.
+# - #utc (aliased as #gmtime): Converts time to UTC in place.
+# - #localtime: Converts time to local time in place.
+#
+# === Methods for Rounding
+#
+# - #round:Returns a new time with subseconds rounded.
+# - #ceil: Returns a new time with subseconds raised to a ceiling.
+# - #floor: Returns a new time with subseconds lowered to a floor.
+#
+# == Timezone Argument
+#
+# A timezone argument must have +local_to_utc+ and +utc_to_local+
+# methods, and may have +name+, +abbr+, and +dst?+ methods.
+#
+# The +local_to_utc+ method should convert a Time-like object from
+# the timezone to UTC, and +utc_to_local+ is the opposite.  The
+# result also should be a Time or Time-like object (not necessary to
+# be the same class).  The #zone of the result is just ignored.
+# Time-like argument to these methods is similar to a Time object in
+# UTC without subsecond; it has attribute readers for the parts,
+# e.g. #year, #month, and so on, and epoch time readers, #to_i.  The
+# subsecond attributes are fixed as 0, and #utc_offset, #zone,
+# #isdst, and their aliases are same as a Time object in UTC.
+# Also #to_time, #+, and #- methods are defined.
+#
+# The +name+ method is used for marshaling. If this method is not
+# defined on a timezone object, Time objects using that timezone
+# object can not be dumped by Marshal.
+#
+# The +abbr+ method is used by '%Z' in #strftime.
+#
+# The +dst?+ method is called with a +Time+ value and should return whether
+# the +Time+ value is in daylight savings time in the zone.
+#
+# === Auto Conversion to Timezone
+#
+# At loading marshaled data, a timezone name will be converted to a timezone
+# object by +find_timezone+ class method, if the method is defined.
+#
+# Similarly, that class method will be called when a timezone argument does
+# not have the necessary methods mentioned above.
 class Time
   # Creates a new \Time object from the current system time.
   # This is the same as Time.new without arguments.