Here is a tool for administrators and webmasters to convert the UNIX Timestamp to Universal Time, Coordinated (UTC). In casual use, UTC is the same as Greenwich Mean Time (GMT) without the offset of Daylight Saving Time (DST). The UNIX Timestamp or UNIX epoch time is the number of seconds elapsed since January 1, 1970. The resulting date will be printed in ISO 8601 Standard (YYYY-MM-DD hh:mm:ss). Your local time is a positive or negative offset from UTC. Local time is UTC plus or minus the time zone offset, +1 for DST.
The first edition UNIX Programmer's Manual defines the UNIX Time measured in sixtieths of a second. One of the first UNIX versions had a 32 bit integer, incrementing at a rate of 60 Hz (sixtieths of a second). Then it was changed to 1 Hz or one second. 32 bit is only about 2.5 years at 60 Hz, but about 68 years in one second steps. Only 68 years will work and not 136 years because the first of these bits is used for the positive/negative sign of the integer, while the remaining 31 bits are used to store the number itself. So the range of the UNIX Timestamp is 0 to 2147483647.

2³² = 4294967296, 2³¹ = 2147483648

The total range is -2147483648 (1901-12-13 20:45:52) to 2147483647 (2038-01-19 03:14:07). When a signed integer reaches its maximum value and then gets incremented, it wraps around to its lowest possible negative value.
In this case to -2147483648 (1901-12-13 20:45:52), so the 19th of January 2038 will suddenly become the 13th of December 1901. The so-called YEAR 2038 PROBLEM is not easy to be solved! Changing to an unsigned 32 bit integer would allow timestamps to be accurate until the year 2106, but would affect many programs that deal with time differences. Changing to an unsigned 64 bit integer would last about 290 billion years, but would break binary compatibility for software, data storage, and anything dealing with binary time.

Time Zone Examples:
New York time zone offset is -5 hours in winter and -4 hours in summer.
London (GMT) time zone offset is 0 in winter and +1 hour in summer.
Berlin time zone offset is +1 hour in winter and +2 hours in summer.

Enter UNIX Timestamp to convert to UTC:    

Resultant UTC from number entered:  1970-01-01 00:00:00
UTC when page loaded:  2008-11-20 13:36:28
Timestamp when page loaded:  1227188188