- Available conditions : 'BEFORE', 'AFTER' ('EQUAL TO' removed for now)
- User input date is guessed by using dateutil parser.
- Input date or date from *.ics files are always converted to datetime
if not time is specified and made offset-aware based on local_timezone
variable defined (for now) on top of the file.

- Add 'DTSTART' & 'DTEND' filter type (Dummy for now)
- Update filter conditions based on filter type.