pastime, past time, passed time

Pastime or pastime ( one word ) means an amusement, sport, hobby, or recreation--something done in one's leisure time--
Baseball is often called America's favorite pastime.
His usual pastime is working in the garden, but he's watching the game on TV today.

Past time or past time ( two words ) means beyond the limits of ( past ) a set hour ( time )--
It's past time for him to be home--he's usually here by six.
It's nine--past time for school to start.

Passed time or passed time means spent or lived through ( passed ) a certain number of minutes, hours, or days ( time )--
While they waited, they passed time talking about their homes.
They passed time playing cards, to keep from being bored.

Now that you know that, you can say--
"He passed time working on his favorite pastime until it was past time for bed."

Note--"times past" means in a long-ago time, perhaps remembered by an old person, perhaps the historical past--
In times past we walked to school for miles, uphill both ways.
"Past times" means the historical past; long ago--
In past times  they only had candles to see by at night.
Note # 2--"time's passed" means a certain number of hours, minutes, or days has ( "time's" meaning time has ) gone by or elapsed ( passed )--
Has it been twenty years? The time's passed so quickly!
"Time's past" means a specific amount of time, or time set aside for a purpose, is ( "time's" would be short for time is, or time has ) used up or gone by--
Hand in your papers now, the time's past.
Note # 3--"pastimes" is the plural ( more than one ) of "pastime", meaning a hobby or recreational activity--
Football and baseball are two of America's favorite pastimes.