A time in one's life looked back upon with great fondness. Usually invokes a memory of a particularly memorable or traumatic incident.

a wednesday a long time ago.

Referring to a time period previous to the present, usually recalled with a somewhat blissful vision.

Reminiscing, remembering fun times, remembering a time when life was more simple

Completely meaningless phrase which has gained inexplicable global popularity. It's an incomplete thought: Back in what day? It's a redundant way of saying "Once, I..." or "I used to..." and adds words without adding any extra meaning. Similar to the equally pointless "at the end of the day..." popularised by English soccer stars.

something from the past, sometimes from one's younger years, or the beginning of something.

Completely meaningless phrase which has gained inexplicable global popularity. It's an incomplete thought: Back in what day? It's a redundant way of saying "Once, I..." or "I used to..." and adds words without adding any extra meaning. Similar to the equally pointless "at the end of the day..." popularised by English soccer stars.