Once upon a time,
B1Long ago (informal)
Back then,
B1In that past time
Years ago,
B1Many years in the past
Previously,
B1Before the current time
Earlier,
B1Before a specific time
At that time,
B1During a specific past moment
During that period,
B1Throughout a specific past time
In those days,
B1In the past (often refers to a specific era)
That day,
B1On a specific day in the past
On that occasion,
B1During a specific past event
I remember when...
B1Recalling a past event
I recall...
B1To remember something from the past
It happened that...
B1Describing a past event
As I recall,
B1According to my memory
To the best of my memory,
B1As far as I can remember
If I remember correctly,
B1Checking the accuracy of memory
From what I remember,
B1Based on my recollection
In retrospect,
B1Thinking about the past now
I used to...
B1Habit in the past
I would...
B1Habit in the past
Many years have passed since...
B1A long time has elapsed since a past event.
Looking back on it,
B2Reflecting on a past event.
In retrospect,
B2Considering something after it has happened.
As I recall,
B2Remembering something from the past.