前 once pictured a foot (止) in a boat (舟) — moving FORWARD across the water. The shape simplified over time, but the idea of 'ahead / in front' stayed.
前 covers both space and time. In SPACE it's 'front': 前面 (in front), 前门 (front door). In TIME it's 'before/ago': 以前 (before/in the past), 前天 (the day before yesterday — pairs with 天). Chinese pictures the past as in FRONT of you (you can 'see' what already happened) and the future behind — the opposite of the English mental map.
A foot in a boat moving ahead — FRONT, BEFORE.
前天 = the day before yesterday, 后天 = the day after tomorrow. Chinese stacks 前/后 (front/back) onto 天 to move along the calendar.