Format Timestamps in Parquet Files Online
Reformat timestamp and date columns in Parquet files directly in your browser. Convert between ISO 8601, Unix epoch, US date, and custom strftime patterns — no upload required.
How to format Timestamps in Parquet files
- Drop your file onto the upload area. The first 200 rows are shown, and the first date or timestamp column is pre-selected if the file has one.
- Pick the column to format. The dropdown shows each column's detected type, and the output column name defaults to the column name plus _formatted.
- Choose the input format: Auto-detect for ISO-style text, Unix epoch in seconds or milliseconds, or a custom strptime pattern such as %d/%m/%Y.
- Choose the output format: ISO 8601, date only, US date, Unix epoch seconds or milliseconds, or a custom strftime pattern. Then click Format Timestamps.
- Check the result preview and download the file. The formatted column replaces the original in the same position.
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 set of temperature sensors logs readings with slightly different timestamp styles, and one device writes "n/a" when its clock has not synced. A US reporting template needs plain MM/DD/YYYY dates.
Input (Parquet)
Parquet file (binary, columnar) — shown as a table with its schema
| sensor_id | event_time | temp_c |
|---|---|---|
| S-01 | 2026-04-11 08:15:32 | 18.4 |
| S-02 | 2026-04-11T23:59:59 | 17.9 |
| S-01 | 2026-04-12 00:00:05 | 18.1 |
| S-03 | n/a | 19.2 |
Schema: sensor_id VARCHAR, event_time VARCHAR, temp_c DOUBLE
Settings
- Column to format: event_time (VARCHAR)
- Output column name: event_time_formatted (default)
- Input format: Auto-detect
- Output format: US date (01/15/2024)
Result
| sensor_id | event_time_formatted | temp_c |
|---|---|---|
| S-01 | 04/11/2026 | 18.4 |
| S-02 | 04/11/2026 | 17.9 |
| S-01 | 04/12/2026 | 18.1 |
| S-03 | NULL | 19.2 |
Auto-detect reads both the space and the T separator as timestamps. The US date output keeps only month, day and year. "n/a" cannot be read as a time, so it becomes empty rather than stopping the run. The original event_time column is replaced by event_time_formatted in the same position, so keep a copy if you need both.
Working with Parquet files
Parquet timestamp columns already carry a real TIMESTAMP or DATE type, so Auto-detect needs no parsing. The column is pre-selected and every value converts. Formatting outputs to ISO 8601, date only, US date or a custom pattern produce a text column, which changes the schema. Downstream tools that expect a timestamp type will see a string instead. Epoch outputs produce a BIGINT column.
Parquet can store timestamps in milliseconds, microseconds or nanoseconds. The ISO 8601 output drops fractional seconds, and Unix epoch seconds is rounded to the nearest whole second. Use epoch milliseconds or a custom pattern with %f if you need sub-second detail. Integer columns holding epoch values, common in event pipelines, can be read with the epoch seconds or epoch milliseconds input options. Pick the one that matches the magnitude: ten digits for seconds, thirteen for milliseconds. DATE columns work too. They are treated as midnight, so outputs that include a time show 00:00:00. Timestamp columns stored with a time zone are converted to UTC first.
Frequently Asked Questions
Will formatting a Parquet timestamp column change its type?
Yes. Text outputs such as ISO 8601 or US date turn the column into a string column, and the epoch outputs turn it into BIGINT. Keep a copy of the original file if other systems need the TIMESTAMP type.
How do I turn an INT64 epoch column in Parquet into readable dates?
Select the column, choose Unix epoch seconds or milliseconds as the input format, and pick ISO 8601 or date only as the output. Check the digit count first: 13-digit values are milliseconds.
What happens to values that cannot be read as a timestamp?
With Auto-detect they become empty (NULL) and the rest of the column is converted. With a custom strptime pattern, any value that does not fit the pattern stops the run with an error, so the file is not half converted.
Does the tool keep the original column?
No. The formatted column replaces the original in the same position, under the output column name you set. Keep your original file if you need both versions.
Which time zone are the results in?
UTC, whatever time zone your computer uses. Epoch seconds and epoch milliseconds are both read as UTC. In Auto-detect, a value with an offset or Z, such as 2026-04-11T08:15:32+02:00, is converted to UTC. A value without an offset is kept exactly as written.
Is there a European DD/MM/YYYY output option?
Not as a preset. Choose Custom pattern (strftime) as the output and enter %d/%m/%Y. The same field takes any strftime tokens, such as %d %b %Y for 11 Apr 2026.
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