Fix for zip file DST 1980 datetime issue.
Fix for zip file DST 1980 datetime issue.

Fix for issue where zipfile.py raises "ZIP does not support
timestamps before 1980" exception. This seems to occur due to
issues with DST not being defined. The fix hardcodes the 1/1/1980
timestamp.

Issue #535

jmcnamara/XlsxWriter,jmcnamara/XlsxWriter,jmcnamara/XlsxWriter,jmcnamara/XlsxWriter