{"id":13160,"date":"2026-09-26T07:35:00","date_gmt":"2026-09-26T05:35:00","guid":{"rendered":"https:\/\/www.lukaswojcik.com\/blog\/?p=13160"},"modified":"2026-10-26T13:32:49","modified_gmt":"2026-10-26T12:32:49","slug":"tutorial-the-five-timestamp-formats-in-a-tracking-stack-and-how-to-convert-between-them","status":"publish","type":"post","link":"https:\/\/www.lukaswojcik.com\/blog\/en\/digital-analytics\/tutorials\/tutorial-the-five-timestamp-formats-in-a-tracking-stack-and-how-to-convert-between-them\/","title":{"rendered":"Tutorial: The Five Timestamp Formats in a Tracking Stack and How to Convert Between Them"},"content":{"rendered":"

A tracking event can appear as Unix seconds, milliseconds, microseconds or text with a UTC offset. An offset states the difference from UTC; +02:00 means two hours ahead. At 12:00 UTC, a clock with the +02:00 offset shows 14:00. Reports also store calendar dates. Reliable conversion requires three facts: the unit, the meaning of the field and the intended time zone.<\/p>\n

Browser time, container start, event time and receipt time do not automatically describe the same instant. Comparing numbers only makes sense after comparing those meanings. Digit count provides a clue, not a field definition.<\/p>\n

\"Timestamp
Explicit units identify the numeric representation. Time-zone rules determine local day boundaries; field semantics remain a separate question.<\/figcaption><\/figure>\n

1. Five common representations<\/h2>\n

The examples below refer to 2026-09-26T23:30:00Z<\/code>, which is 01:30 on 27 September 2026 in Berlin. Only the first three formats count units from the Unix epoch, 1 January 1970 at 00:00 UTC. ISO notation expresses calendar fields; a date alone does not identify an instant.<\/p>\n
Representation<\/th>Example<\/th>Meaning<\/th><\/tr><\/thead>
Seconds<\/td>1790465400<\/td>Unix seconds; for example Meta event_time<\/td><\/tr>
Milliseconds<\/td>1790465400000<\/td>Unix milliseconds; for example Date.now()<\/td><\/tr>
Microseconds<\/td>1790465400000000<\/td>Unix microseconds; for example GA4 event_timestamp<\/td><\/tr>
ISO 8601 \/ RFC 3339<\/td>2026-09-27T01:30:00+02:00<\/td>Calendar fields with an explicit offset<\/td><\/tr>
Calendar date<\/td>20260927<\/td>Berlin date in this example, not an instant<\/td><\/tr><\/tbody><\/table>\n

Date.now()<\/code> returns milliseconds from the current system clock. In the standard GTM installation, gtm.start<\/code> records container initialization, not every subsequent click. A correct unit can therefore coexist with an incorrect interpretation.<\/p>\n

For values from 2026, ten, 13 and 16 digits are typical of seconds, milliseconds and microseconds. Older or negative timestamps, other epochs and ordinary identifiers do not fit this recognition rule. Eight digits also do not establish a valid date: 20260230<\/code> is not a calendar day.<\/p>\n

2. Conversion with an explicit unit<\/h2>\n

The function accepts integers or strings of decimal digits with an optional sign. Value and unit are separate arguments. Floating-point numbers, booleans and decimal-fraction strings are rejected to prevent unnoticed rounding. Nanoseconds are accepted only when conversion to microseconds is exact.<\/p>\n

Python<\/span>