Don't advance to dayOfWeek if it is 0

If 24:00 is used with a specific day, it will advance to next Monday, since advance is set to true and dayOfWeek is updated to 1.

To fix #173:
1, don't set advance to true if dayOfWeek is 0.
2, don't update dayOfWeek if it is 0.
Merge pull request #182 from longhua/fix_#173

Don't advance to dayOfWeek if it is 0

See #182