Added check for date-formats

[RyanWalker277]

Fixes #1020

Code changes

Added a function to check if an input date_string belongs to specefied date_formats or not

Help Required

Even though I did an extremely small code change , It is failing some tests. Can any of the available maintainers help me determine the cause?

cc - @Gallaecio

[RyanWalker277]

Hey @Gallaecio , I have fixed the test cases issue. It is now passing all the test cases. Kindly review it.