@staticmethod<EOL><INDENT>def diff_in_days(start, end):<DEDENT>
diff = from_ymd_to_excel(*end.date)-from_ymd_to_excel(*start.date)<EOL>return float(diff)<EOL>
calculate difference between given dates in days

:param BaseDateTuple start: state date
:param BaseDateTuple end: end date
:return float: difference between end date and start date in days