These are the small, specific calculations that come up constantly but rarely justify opening a spreadsheet — splitting a bill with tip, converting a timestamp to a readable date, figuring out someone's exact age in days, or converting between units when a recipe or a spec sheet uses a system you don't normally think in.
A genuinely common source of confusion worth clearing up: a Unix timestamp is the number of seconds since January 1, 1970 — it's how most programming languages and databases store a moment in time internally, and it looks nothing like a human-readable date until it's converted. If you've ever seen a number like 1758000000 somewhere in a system log or API response and wondered what it meant, that's exactly this.
Time zone conversion trips people up for a specific, avoidable reason: daylight saving time isn't observed the same way everywhere, so a fixed offset (like "UTC-5") isn't actually fixed year-round in places that observe DST. Our time zone converter accounts for this automatically rather than assuming a static offset.