Default reminder time could be used to trigger an alarm

[0xC0FFEEC0DE]

The app has a setting for "default reminder time": "At the deadline", "0.5 days before", "1 day before", ... This setting currently is used only for the color of the not-done tasks: blue (task is far away), orange (default reminder time is in the past), red (task is in the past)

I think the default reminder should trigger an alarm, the same as the user-set reminder time.

But currently the deadline gets chosen only as a date, not as date plus time. This results in a time at day of 00:00. So an alarm at default reminder time of "1 day before" would occur at midnight, which is not OK.

So enabling alarms together with default reminder time would require the following:

• Deadline date picker gets changed to date-time-picker
• If user does not set a reminder time but a deadline it shall be set automatically based on deadline and default reminder time

Does that sound good?

[0xC0FFEEC0DE]

Applied default reminder timespan differently: It gets used to preset the calendar when the user opens it to set the reminder time:

• If previously a reminder time was set the calendar gets set to it
• Else if a deadline is set the calendar gets set to deadline minus default reminder timespan (or now + 1h, if this is in the past)
• Else the calendar gets set to now plus default reminder timespan

See also #3