Parse Dates in Parquet Files Online
Parse and convert date columns in Parquet files between formats and timezones directly in your browser. Supports ISO 8601, US/EU dates, Unix timestamps, and custom patterns — no upload required.
How to parse Dates in Parquet files
- Drop your file. The first column is preselected, and the output name defaults to that column name plus _parsed.
- Pick the column to parse. The list shows each column's detected type, so you can see whether it is already a DATE or TIMESTAMP or still text.
- Choose the input format: Auto-detect, ISO 8601, US date (MM/DD/YYYY), EU date (DD/MM/YYYY), Unix epoch in seconds or milliseconds, or a custom strptime pattern.
- Leave both timezones on UTC unless you need a conversion, then pick an output format: ISO 8601, date only, US date, EU date, Unix epoch seconds, or a custom strftime pattern.
- Click Parse Dates, check the preview, and download. The parsed column replaces the original column in the same position. A message tells you how many values could not be parsed.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
A hotel booking system exports check-in times as ISO-style timestamps. The UK finance team wants plain DD/MM/YYYY dates, and one booking still has "TBC" instead of a date.
Input (Parquet)
Parquet file (binary, columnar) — shown as a table with its schema
| booking_ref | guest_country | check_in | nights |
|---|---|---|---|
| HB-5520 | IE | 2026-09-14 15:00:00 | 3 |
| HB-5521 | DE | 2026-09-15 11:30:00 | 1 |
| HB-5522 | FR | TBC | 2 |
| HB-5523 | GB | 2026-10-02 18:45:00 | 5 |
Schema: booking_ref VARCHAR, guest_country VARCHAR, check_in VARCHAR, nights BIGINT
Settings
- Column to parse: check_in
- Output column name: check_in_parsed (the default)
- Input format: Auto-detect
- Source and target timezone: UTC (no conversion)
- Output format: EU date (15/01/2024 style)
Result
| booking_ref | guest_country | check_in_parsed | nights |
|---|---|---|---|
| HB-5520 | IE | 14/09/2026 | 3 |
| HB-5521 | DE | 15/09/2026 | 1 |
| HB-5522 | FR | NULL | 2 |
| HB-5523 | GB | 02/10/2026 | 5 |
check_in is replaced by check_in_parsed in the same position, and the other columns are untouched. Auto-detect reads the timestamps and the EU output keeps only the date. "TBC" is not a date, so it becomes NULL instead of stopping the run, and the tool reports 1 value that could not be parsed. The new column is text, because DD/MM/YYYY is a display format rather than a date type.
Working with Parquet files
Parquet date and timestamp columns are already typed, so they are used directly and the input format does not matter. A DATE is treated as midnight. The tool is most useful on Parquet for columns that hold time as numbers. Event pipelines often write an INT64 count of milliseconds since 1970, and the Unix epoch (milliseconds) mode reads those directly.
Every output format except epoch seconds produces a string. Parsing a typed timestamp column therefore changes the file schema: the column is renamed and becomes VARCHAR. That matters if another job reads the file with a fixed schema. If you want a typed column back, parse to ISO 8601 and then cast the result to TIMESTAMP with Cast Column Types, which reads the 2026-09-14T15:00:00 form.
Frequently Asked Questions
How do I turn an epoch milliseconds column in Parquet into readable timestamps?
Select the column, choose Unix epoch (milliseconds) as the input and ISO 8601 as the output. 1788345000000 becomes 2026-09-02T10:30:00. The result is a string column.
Will parsing change my Parquet schema?
Yes. The chosen column takes the output name and becomes a string, or a BIGINT for epoch seconds output. All other columns keep their names and types.
What happens to values that cannot be parsed?
They become empty (NULL) in every mode, and the rest of the column is parsed. After the run the tool tells you how many values failed, so you can check them. Empty cells are not counted as failures.
How does the time zone conversion work?
The source zone is where the times were recorded, and the target zone is the one you want. 14:00 US/Eastern in July becomes 18:00 UTC, and 14:00 in January becomes 19:00 UTC, because daylight saving time is applied. Unix epoch values are always read as UTC, whatever the source zone says.
Does the tool keep the original column?
No. The parsed values replace the source column in the same position, under the output column name. Keep a copy of the original file if you need both.
What type is the parsed column?
Text for every output format except Unix epoch seconds, which is a whole number. ISO 8601 output looks like 2026-09-14T15:00:00 and date-only output like 2026-09-14. Cast the column to DATE or TIMESTAMP afterwards if you need a typed column.
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