Editing Iranian calendars (section)

==Muslim conquest==

The Muslim rulers who took over from the middle of the seventh century used the [[Islamic calendar]] for administration, which caused hardship because the year was shorter – i.e. a tax which was formerly collected after the harvest would now have to be paid before the harvest.   Traditionally it is said that the [[Caliph]] [[Umar|Omar]] reintroduced the Persian calendar for tax collection purposes.{{citation needed|date=April 2017}}

In AD 895 there was another double readjustment of the start of the ''araji'' year.   It moved from 1 Frawardin (12 April) to 1 Khordad (11 June).   By AD 1006 the vernal equinox, 15 March, was again coinciding with ''nowruz'', 1 Frawardin.   In that year, therefore, the ''epagomenai'' were delayed four months, moving from the end of Aban to their old position at the end of Spandarmad.   This is the calendar for AD 1006/7:

{|class="wikitable" style="float:centre"
|+ * denotes 1 Epagomene
!Armenian<br />month||First day||Old<br />Egyptian<br />month||First day||Persian<br />month||First day
|-
|1||15*–20 March||4||15 March||1||10*–15 March
|-
|2||19 April||5||14 April||2||14 April
|-
|3||19 May||6||14 May||3||14 May
|-
|4||18 June||7||13 June||4||13 June
|-
|5||18 July||8||13 July||5||13 July
|-
|6||17 August||9||12 August||6||12 August
|-
|7||16 September||10||11 September||7||11 September
|-
|8||16 October||11||11 October||8||11 October
|-
|9||15 November||12||10 November||9||10 November
|-
|10||15 December||1||10*–15 December||10||10 December
|-
|11||14 January||2||14 January||11||9 January
|-
|12||13 February||3||13 February||12||8 February
|}

The ''gahanbar'' did not move quite to their old places, because the fifth moved to 20 Day, which was the old 15 Day, thus increasing the interval between the fourth and fifth to eighty days and reducing the interval between the fifth and sixth to 75 days.   The new dates were:

{|class="wikitable" style="float:centre"
|-
!No.||Name||Date||Time since previous
|-
|1||maidyozarem||(11-) 15 ii (Ardawahisht)||45 days
|-
|2||maidyoshahem||(11-) 15 iv (Tir)||60 days
|-
|3||paitishahem||(26-) 30 vi (Shahrivar)||75 days
|-
|4||ayathrem||(26-) 30 vii (Mihr)||30 days
|-
|5||maidyarem||(16-) 20 x (Day)||80 days
|-
|6||hamaspathmaidyem||(1-) 5 Epagomene||75 days
|}