Overview
Introduction
Dates pulled from spreadsheets, forms, or logs often arrive in whatever order they were entered rather than chronological order.
This tool sorts a plain list of calendar dates ascending, while also catching any date in the list that isn't actually valid.
What Is Sort Calendar Dates?
A line-based calendar date sorter: paste one YYYY-MM-DD date per line and get the same list back sorted from earliest to latest.
Every date is fully validated, including correct day counts per month and per leap year, before it's included in the sort.
How Sort Calendar Dates Works
Each line is matched against the YYYY-MM-DD pattern and its year, month, and day are checked against real calendar bounds, including the standard leap-year rule.
Valid dates are converted to a single sortable number (year*10000 + month*100 + day) for comparison, then the original line text is written back out in sorted order.
When To Use Sort Calendar Dates
Use it to put a scattered list of dates, deadlines, event dates, log entries, into order before reading through them.
It also doubles as a batch validator: if any line is malformed or refers to a date that doesn't exist, the whole list is rejected with a specific reason.
Often used alongside Sort Date Intervals, Validate a Calendar Date and Truncate a Calendar Date.
Features
Advantages
- Explicit leap-year and per-month day-count checks catch invalid dates instead of silently accepting them.
- Preserves the exact original text of each date in the sorted output.
- Handles dates across any range of years, not just the current one.
Limitations
- Requires strict YYYY-MM-DD formatting, other date formats must be converted first.
- All-or-nothing validation: one invalid line stops the whole sort rather than skipping just that line.
Examples
Best Practices & Notes
Best Practices
- Convert any non-ISO date formats (like MM/DD/YYYY) to YYYY-MM-DD before pasting them in.
- If a date is rejected, check Calendar Date Validator on that single line for a detailed explanation of what's wrong.
Developer Notes
Validation shares its day-count table and leap-year formula ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0) with Calendar Date Validator and Calendar Date Truncator; sorting uses a plain numeric comparator on a year*10000+month*100+day key rather than constructing Date objects, avoiding any timezone-related surprises.
Sort Calendar Dates Use Cases
- Putting a list of project deadlines or milestones into chronological order
- Ordering event dates pulled from a form export before building a timeline
- Validating and sorting a batch of birthdates or anniversaries at once
Common Mistakes
- Pasting dates in MM/DD/YYYY or DD/MM/YYYY format, which don't match the required YYYY-MM-DD pattern.
- Including a date that looks plausible but doesn't exist, like April 31st or a February 29th in a non-leap year.
Tips
- For date ranges rather than single dates, use Date Interval Sorter so the start and end stay paired together.
- Truncate a list to month or year first with Calendar Date Truncator if you only need to sort by bucket, not exact day.