Acronym Soup: AOBTD?

Questions

during the cambrian period, about ---------- years ago, a day was only 20.6 hours long?

during the cambrian period, about 500 million years ago, a day was only ---------- hours long?

during the---------- , banks first used scotch tape to mend torn currency?

during the depression, ---------- first used scotch tape to mend torn currency?

during the depression, banks first used ---------- tape to mend torn currency?