[tz] More historical data for Iran

[Roozbeh Pournader]

Two more pieces of information about historical timezone changes in Iran,
this time in the late 1970s:

I just ran into an academic paper that looks into the psychology of
daylight savings in Iran, and it has the exact times for the change in 1977
and the beginning of the change in 1979 (but not its end, unfortunately).

https://www.jstor.org/stable/178704

Here's the quotes from the paper:
1. '"Iran's official time keeper moved the clock one hour forward as from
March 22, 1977 (Farvardin 2, 2536) to make maximum use of daylight and save
in energy consumption. Thus Iran joined such other countries as Britain in
observing what is known as 'daylight saving.' The proposal was originally
put forward by the Ministry of Energy, in no way having any influence on
observing religious ceremonies. Moving time one hour forward in summer
means that at 11:00 o'clock on March 21, the official time was set as
midnight March 22. Then September 24 will actually begin one hour later
than the end of September 23 [...]." Iran's time base thus continued to be
Greenwich Mean Time plus three and one-half hours (plus four and one-half
hours in summer).'

The article sources this from Iran Almanac and Book of Facts, 1977, Tehran:
Echo of Iran, which is on Google Books at
https://www.google.com/books/edition/Iran_Almanac_and_Book_of_Facts/9ybVAAAAMAAJ.
(I confirmed it by searching for snippets.)

2. "After the fall of the shah, the revolutionary government returned to
daylight-saving time (DST) on 26 May 1979."

This seems to have been announced just one day in advance, on 25 May 1979.

The change in 1977 clearly seems to be the first daylight savings effort in
Iran. But the article doesn't mention what happened in 1978 (which was
still during the shah's government), or how things continued in 1979
onwards (which was during the Islamic Republic).

This data doesn't seem to match tzdata: First, an entry for 1977 needs to
be added, for which we seem to have complete data. Second, the beginning of
daylight saving time in 1979 needs to be changed to May 26.

Thanks,
Roozbeh
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