Iran Official Date And Time (Jalali calendar - Tehran TimeZone) Solution in SQL raw and linq query (ef core 5).

IranOfficialDateAndTimeInSQLServer.sql

declare @myutcdate as datetime2 = CAST('2021-03-17 22:00' AS datetime2);

select 
FORMAT(SWITCHOFFSET(@myutcdate, '+03:30'), 'yyyy-MM-dd', 'fa') as 'get iran date',
FORMAT(SWITCHOFFSET(@myutcdate, '+03:30'), 'yyyy-MM', 'fa') as 'get iran year-month',
CAST(FORMAT(SWITCHOFFSET(@myutcdate, '+03:30'), 'dd', 'fa') as int) as 'get iran day',
CAST(FORMAT(@myutcdate, 'dd', 'fa') as int) as 'invalid time-zone results in invalid date.'

test performance on about 4m records

--select RecievedDateTime from Table -- 00:11

--select Format(RecievedDateTime , 'yyyy-MM-dd') from Table -- 00:44

--select dbo.GregorianToJalali(RecievedDateTime , 'yyyy-MM-dd') from Table -- 03:42

--select Format(RecievedDateTime , 'yyyy-MM-dd', 'fa') from Table -- 03:47

--select dbo.GregorianToJalali(RecievedDateTime , 'MM') from Table -- 03:35

--select Format(RecievedDateTime , 'MM', 'fa') from Table -- 01:54

--select Format(RecievedDateTime , 'yyyy-MM', 'fa') from Table -- 02:33

--select Format(SWITCHOFFSET(RecievedDateTime, '+03:30'), 'yyyy-MM', 'fa') from Table -- 02:33

--select Left(RecievedDateTime_Iran_StoredComputedColumn, '7') from Table -- 00:12 -- getting yyyy-MM

Format function is not deterministic and cannot be used in StoredComputedColumns. so for last select we should use GregorianToJalali or another way.