I’ve got an old iMac, running OS 9.1. It’s suddenly started to re-set its clock to a date in August, 1958, every time I turn it on. Anyone have any suggestion what the problem is, and what I can do to fix it?
Thanks.
Replace the PRAM battery.
3.6v lithium.
Be aware that doing that is a pain in the ass.
Yeesh. My old Mac Plus just had a little slot that opened and took an AA. I guess this is progress.
With the later iMacs, the battery can be accessed through the RAM door, but it’s a bit tricky. A long hemostat or tweezer may help. I do this all the time.
Just a note that this problem is not limited to Macs: PC’s have similar issues, and will time travel back to 1980 if their lithium battery dies.
Mac trivia: the default date for the clock in 1958 is the birthdate of the engineer who developed it.
My Macs have usually reverted to 1909 when they lose PRAM-battery support. I think there was some reason for the switch to 1956 but I don’t recall what it was.
My old Macs used to revert to the 50’s & 60’s when the pram battery went dead too. I always wondered why they reverted to a time well before their manufacture date. Macs are just hippies at heart, I guess.
In general, the hardware clock on a computer is a register that counts seconds starting from zero. Zero has to be something, so when losing the battery, the register resets to zero and you’re back at the dawn of time.