Possible Clues:

• Sunless weeks perhaps this old poet's woe!
• Unfortunately dated leap years certainly don't!
• Not be able to arrange a date, alas?
• Be short of time, unfortunately
• Have no time, unfortunately
• For instance, no Sun. in short? Oh dear!
• Current diaries do, compared to their predecessors, alas!
• What busy vacations seem to do, unfortunately
• Woe is me, that leaves me one day short!
• Miss a moment of glory, hence expression of regret