of all times; of all days
Expresses exasperation or irony that something happens at an especially bad or inconvenient moment. Often followed by a negative or undesirable event.
Of all days, the train had to be late on the day of an important meeting.
Of all times, he came to visit right in the middle of moving.
Variant with okurigana; both spellings are used.
From 折 (opportunity/time) + も (even) + あろう (volitional of ある) + に (particle), literally 'even though there must be other times'.