useless trivia: What Word Means: Pertaining To Or Having Existence?

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.?