The Longest Day

The Longest Day is a pet battles achievement awarded for completing 41 pet battle daily quests within one daily quest reset period.

Players only need to complete either the Alliance or the Horde Azeroth daily quests, not both, to satisfy the "Azeroth Dailys - A/H" criterion.

Tips
The timer starts when the first quest is turned in, so fill up the quest log with completed difficult quests, then as soon as possible after the daily quest reset time, turn in as many quests as possible while working on the remainder.