set new deadline with seconds -> not allowed / not meaningful error message

[Tobias-Horstmann]

If you want to edit a deadline you are able to set the time precisly to seconds, in the pop up window when clicking on the time field there is even a sliding bar to set the seconds precisly. However, it seems you are not allowed to set a time with seconds differ from 0.

Example
a) If you set the time to a value with specified seconds (not set to :00), for example 23:59:20 instead of 23:59:00 an error message is given "The input is not a valid step".

b) expected behaviour: time could be set even if seconds are not set to zero value or error message tells you that for seconds only "00" is allowed and in this case it would be useful if the sliding bar for seconds in the pop up window would be removed.

[kskwared]

Seems to be a low priority, because only admins will use this feature and they can manage by not setting non-seconds values of deadlines.