In SQL Сервер
Declare @S varchar(50) = '25MAR2019:00:00:00.000'
Select AsString = convert(varchar(10),try_convert(date,stuff(stuff(left(@S,9),6,0,' '),3,0,' ')),110)
,AsDate = try_convert(date,stuff(stuff(left(@S,9),6,0,' '),3,0,' '))
Возвращает
AsString AsDate
03-25-2019 2019-03-25