Definitions:

1. An expression meaning a very long time ago, or the beginning of time, often used humorously or vaguely when the exact date isn't known or isn't important. NOUN
   • I've been waiting since the year dot for them to fix that leak.
2. Implies something is extremely old, ancient, or long-lasting. NOUN
   • From year dot, humans have always possessed an innate curiosity to explore their surroundings.
3. Used to exaggerate how long something has existed or been happening. NOUN
   • She's live in that house since the year dot.

Synonyms:

• from the beginning
• since forever
• since the dawn of time