Random Day Generator
Generate a random day of the week, or a random day-of-month number (1-31).
How the random day generator works
This tool picks a day using crypto.getRandomValues(), your browser's cryptographically secure random source, with rejection sampling so every outcome has exactly equal probability (no modulo bias). Choose "Day of the week" to get an unweighted pick from Sunday through Saturday, or "Day of the month" to get a random whole number from 1 to 31 — handy for picking a random weekday for a task, a random date-of-month for a recurring billing or reminder rule, scheduling fairness (e.g. whose turn is it this week), games, giveaways, or any scenario where you need an unbiased day picked without checking a real calendar. Everything runs locally in your browser and nothing is sent anywhere.
Note that "day of the month" always generates a number from 1-31 regardless of the actual month length, since this is a generic random-number picker rather than a calendar-aware date generator — for months with fewer days (like February), you may want to re-roll or cap the range at 28/29/30 yourself.
Built and maintained by Meet Shah · Last updated
What this tool is used for
- Picking a day of the week for a recurring meeting without bias.
- Generating days to populate a test fixture.
- Producing input to exercise weekday and weekend branching.
- Choosing a day-of-month value for a schedule fixture.
- Selecting a day for a rota where nobody should be able to predict the pick.
Frequently Asked Questions
- What exactly is being picked?
- A day of the week, uniformly from the seven names — not a date. Those are different questions: any given date falls on a day determined by the calendar, whereas this is a fresh 1-in-7 draw each time with no calendar involved.
- Which day does the week start on?
- It depends where you are, which is why the question comes up. ISO 8601 and most of Europe start on Monday; the US, Canada and Japan start on Sunday. The pick is uniform either way — the ordering only matters for how the list is displayed.
- Are real events evenly distributed across weekdays?
- Almost never, which is worth remembering before using a uniform pick to model one. Retail sales, hospital admissions, deployments and traffic all have strong weekday patterns, so a uniform draw is the right tool for a fair choice and the wrong one for a realistic simulation.
- Can it exclude weekends?
- Filter the result or draw again — and note that "weekend" is not universal. Friday and Saturday are the weekend across much of the Middle East, and a few countries observe only one day, so a rule hard-coded to Saturday and Sunday is a localisation assumption.
- What is the doomsday rule?
- A method for working out any date's weekday in your head: certain dates in each month — 4/4, 6/6, 8/8, 10/10, 12/12 — always share a weekday within a year, and you count from there. It is the classic party trick behind every mental calendar calculation.
Common errors and gotchas
- Generating a day-of-month above 28 without a month, where the date may not exist.
- Assuming weeks start on the same day everywhere, which differs by locale and by standard.
- Ignoring public holidays, which no random draw will account for.
- Overlooking that weekday numbering is zero-based in some systems and one-based in others.
- Requesting more unique weekdays than seven, which cannot be satisfied and silently repeats.