The authorities in the country or territory you’re travelling to are responsible for setting and enforcing the rules for entry.
If you’re unclear about any aspect of the entry requirements, or you need further reassurance, you’ll need to contact the embassy, high commission or consulate of the country or territory you’re travelling to.
It begins on the vernal equinox (Nowruz) as determined by astronomical calculation for the Iran Standard Time meridian (52.5°E or GMT 3.5h).
This determination of starting moment is more accurate than the Gregorian calendar for predicting the date of the vernal equinox, because it uses astronomical observations rather than mathematical rules.
For a succession of Iranian solar calendars, see Iranian calendars.