Official Iran hour(International Code IRST or IT) compared to Greenwich scheduling with respect to the meridian difference is plus +3:30(UTC +3:30) that is second half of the year is applied and the first half of the year by applying the summer time, solar year goes to forward one hour.
The time was set by the group headed by Dr Mahmoud Hesabi for Iran country. By 1933 solar year, Iran time (clock) has been set to sunset and each city has had a time (clock).
In this year with Dr Mahmoud Hesabi’s effort by calculating longitude and latitude and communication with international Greenwich of official time has been set for the country.
Before official time of Iran, apparently it was customary that clock hand was set on 12 o’clock every morning, every noon and every evening. In other words, at times mentioned, clock (time) is set to zero and a new start is considered to calculate the clock.
For example, 4 o’clock means 4 hours have passed since morning, noon, evening(depending on the time position). In most costs, clock was good afternoon and then good evening that by setting the clock at 12.
It also has a religious application. Every a few days, once exact setting was done. Iran official time, every year in 24 o’clock, first day of March goes an hour forward and 24 o’clock, thirtieth (30th) September returns to back, first mode. To know exact time of iran, click here.