Add dependency to date_utils

[Paul-Todd]

Hi, is there any plan to add a dependency to your date_utils and remove the existing code for date manipulation?

I spotted the DST bug you fixed in the date_utils has impacted this as well (when expanded and in BST (GMT/UTC+1) the day is off by 1.

[ericwindmill]

That is what we should be doing, I can give this some time to fix it tomorrow.

[ericwindmill]

Fixed.