Passed and Past can be awfully tricky, particularly because, unlike most other commonly confused words, they are forms of the same root. So, how do we tell them apart? Excellent question.

Step 1. Define both forms of “pass”

Passed:

• (v.) moved through, ahead, by or past. To be communicated. To cease to exist. Happened. Weathered or achieved. Surpassed or went beyond. Went by without noticing or stopping. Transferred or handed off.

Past:

• (adj.) bygone, no longer current, just elapsed, having served in a official capacity
• (n.) the time before the present, a history or previous background
• (adv.) on or onwards, by, ago, along 

Step 2. Show both versions in action

Examples: Her past was in the past, she thought as the train passed through the station. It was a quarter past four. A man who had just missed a different train hustled past. The stranger resembled a past president, though she couldn’t place which one. The man turned to ask her the time. She glanced at her watch, then passed him the information.

Step 3. Profit