You're Wrong About Dates – and Your Code Is Lying to You

Summary

Every date library you’ve ever used is lying to you. They all pretend that a date is a precise moment — a frozen point on a timeline. 2023? Must mean January 1st at 00:00:00.000 UTC. March 2024? Clearly March 1st, 00:00 UTC. March 15th, 2024? Sure, March 15th at the stroke of midnight. But that’s not how humans think. When you say “2023”, you mean the whole year. “March 2024”? The entire month. Even “March 15th” means the full day, not some arbitrary nanosecond. We’ve been forced into fake precision that doesn’t match reality. And it’s not harmless — it leads to broken logic, messy hacks, and subtle bugs that only show up in production. The Rebellion: Time as Intervals In Decipad, a date isn’t a pinpoint — it’s an interval with a built-in granularity. date(2023) = January 1st to December 31st. date(2023-03) = March 1st to March 31st. date(2023-03-15) = midnight to 23:59:59 that day. Your code instantly understands that a year contains a month, a month contains a day, and an hour contains 60 minutes. Year = date(2023) Month = date(2023-03) Day = date(2023-03-15) Year contains Month // true Month contains Day // true Day contains Month // false This isn’t just “nicer syntax” — it’s a fundamental shift in how your software thinks. The Other Half: Time Intervals If dates are intervals, then the difference between two dates is also an interval. We treat that as a first-class value too. Start = date(2020-02-23) End = date(2020-04-05) Duration = End - Start // 42 days Duration as hours // 1008 hours Duration as minutes // 60,480 minutes This is insanely useful: Project management: ProjectEnd - Today gives you remaining days, instantly. Finance: Q2 - Q1 returns 3 months without you hardcoding days-per-month. Events: A week-long conference? That’s literally a 7 days object — not a magic number in milliseconds. Why This Changes Everything Once you start thinking about time as nested intervals, so many things become intuitive: No more picking random timestamps for “March 2024....