What does "one day" mean?

At some unspecified time in the future.

What is a synonym for "one day"?

Common synonyms include: 24 hours, calendar day, date to come, day, eventually, future date.

adv

adv ·Uncommon ·Advanced level

Adverb

1
At some unspecified time in the future.
"One day I shall upgrade my software, but not just yet."
2
At some unspecified time in the past.
"One day I was playing with a girl from my class."
3
Used other than figuratively or idiomatically: see one, day.
"You can stay one day or two."

"One day I shall upgrade my software, but not just yet."