ERROR while assigning 1800-12-25T00:00:00 to variable type %TimeStamp

Hi Community,

I DTL I am assigning value to %TimeStamp type praport named BirthDate.

18001225  converted to 1800-12-25T00:00:00  but giving below error

ERROR #7208: Datatype value '1800-12-25T00:00:00' is not a valid timestamp format
> ERROR #5802: Datatype validation failed on property 'xxx.xxx.xxxx.xxxxx:BirthDate', with value equal to "1800-12-25T00:00:00"

20000612   converted to 2000-06-12T00:00:00  is not giving any error

Please help me to resolve this. 

* We did not define the variable type as %TimeStamp   , this persistence class created based on XSD.

Thanks 

Prashanth