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Enter dates (one per line, or comma/semicolon separated)

Dates entered: 0 Formats: YYYY-MM-DD, MM/DD/YYYY, DD.MM.YYYY, Month DD YYYY, DD Mon YYYY

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Output Format

Remove duplicates Show gap analysis

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About

Misordered dates cause scheduling conflicts, data corruption in spreadsheets, and compliance failures in audit trails. This tool parses dates from 6 common formats - including YYYY-MM-DD (ISO 8601), MM/DD/YYYY, DD.MM.YYYY, and natural language like January 15, 2024 - normalizes them to epoch milliseconds, and sorts via direct compare(a, b) on timestamp values. Gap analysis computes Δd between consecutive entries in days, exposing missing records or irregular intervals. The parser rejects ambiguous input and flags errors per line. It does not guess ambiguous formats like 01/02/03 without context; you must select the expected format or rely on ISO 8601 for unambiguous results.

Formulas

Sorting operates on epoch milliseconds. Each input string is parsed into a timestamp t via the normalized Date constructor:

t = Date.parse(normalized_string)

The comparator for ascending order:

compare(a, b) = t_a − t_b

Gap between consecutive sorted dates i and i+1:

Δd_i = t_i+1 − t_i86400000

Where t = epoch timestamp in milliseconds, 86400000 = milliseconds per day (24 × 60 × 60 × 1000), and Δd = gap in days between consecutive dates.

Reference Data

Format Name	Pattern	Example	Standard	Region	Sortable Natively
ISO 8601	YYYY-MM-DD	2024-03-15	ISO 8601	International	Yes
US Short	MM/DD/YYYY	03/15/2024	Common US	United States	No
EU Dot	DD.MM.YYYY	15.03.2024	DIN 5008	Germany, Russia	No
EU Slash	DD/MM/YYYY	15/03/2024	Common EU	UK, France, India	No
Long Month	Month DD, YYYY	March 15, 2024	AP Style	English-speaking	No
Short Month	DD Mon YYYY	15 Mar 2024	RFC 2822	International	No
Year-Month	YYYY-MM	2024-03	ISO 8601	International	Yes
US Long	Month DD YYYY	March 15 2024	Informal	United States	No
Compact	YYYYMMDD	20240315	ISO 8601 Basic	International	Yes
Dash EU	DD-MM-YYYY	15-03-2024	Common EU	Europe, Asia	No
Unix Timestamp	Seconds since epoch	1710460800	POSIX	Computing	Yes
Excel Serial	Days since 1900-01-01	45366	Microsoft	Spreadsheets	Yes

Frequently Asked Questions

The string 01/02/2024 matches both MM/DD/YYYY (January 2) and DD/MM/YYYY (February 1). The tool defaults to MM/DD/YYYY (US format) for slash-separated dates unless the first segment exceeds 12, in which case it falls back to DD/MM/YYYY. For unambiguous results, use ISO 8601 format (YYYY-MM-DD) or select the expected format from the format hint dropdown.

The parser normalizes via the native Date constructor, which rolls over invalid dates (e.g., February 30 becomes March 1 or 2 depending on leap year). The tool detects this rollover by comparing the output month to the input month. If they differ, the entry is flagged as invalid with a specific error message and excluded from sorting.

The tool strips time components during parsing and operates on date-only precision. If your input contains timestamps like 2024-03-15T14:30:00Z, the time portion is ignored and the date is treated as 2024-03-15. For time-aware sorting, you would need a datetime-specific tool.

Gap analysis computes calendar days only. It does not account for business days, weekends, or public holidays. A gap of 3 days between Friday and Monday is reported as 3, not 1 business day. For business-day calculations, subtract weekends manually or use a dedicated working-days calculator.

The tool processes up to 10,000 dates in a single batch. JavaScript's Array.sort runs in O(n log n) time. For 10,000 entries, this completes in under 50 milliseconds on modern hardware. LocalStorage limits the persistent cache to approximately 5 MB, which accommodates roughly 50,000 date entries.

By default, sorted results are displayed in ISO 8601 (YYYY-MM-DD) for consistency. You can toggle the output format to match your preferred display style. The original raw input string is preserved internally and shown in the detail view alongside the normalized date.