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Timestamp Format

Time format fields for timestamp_format and rotated log filenames

Table of Contents

Timestamp Format
Date Fields
Time Fields
Offset Fields
Unix Timestamp Field
Common Modifiers
Examples
Error Handling

Timestamp Format

Radiator uses bracketed time format fields for the timestamp_format() filter and rotated-filename patterns. Literal text is copied to the output. Fields are written inside square brackets.

timestamp_format("[year]-[month]-[day]T[hour]:[minute]:[second]")

For example, the format above can produce:

2026-06-24T08:45:12

Date Fields

Field	Description	Example
`[year]`	Calendar year	`2026`
`[month]`	Month number	`06`
`[day]`	Day of month	`24`
`[ordinal]`	Day of year	`175`
`[weekday]`	Day of week	`Wednesday`
`[week_number]`	Week number	`26`

Time Fields

Field	Description	Example
`[hour]`	Hour in 24-hour clock	`08`
`[minute]`	Minute	`45`
`[second]`	Second	`12`
`[subsecond]`	Fractional second	`123456789`
`[period]`	AM or PM marker for 12-hour output	`AM`

Offset Fields

Field	Description	Example
`[offset_hour]`	UTC offset hour	`+03`
`[offset_minute]`	UTC offset minute	`00`
`[offset_second]`	UTC offset second	`00`

Unix Timestamp Field

Field	Description	Example
`[unix_timestamp]`	Unix timestamp in seconds	`1782290712`

Common Modifiers

Add modifiers inside a field after the field name:

[field modifier:value modifier:value]

Common modifiers:

Modifier example	Description
`[subsecond digits:3]`	Output three subsecond digits.
`[offset_hour sign:mandatory]`	Always include `+` or `-` in the offset hour.
`[month repr:long]`	Output the full month name.
`[month repr:short]`	Output the abbreviated month name.
`[weekday repr:long]`	Output the full weekday name.
`[weekday repr:short]`	Output the abbreviated weekday name.
`[year repr:last_two]`	Output the last two digits of the year.
`[hour repr:12]`	Output a 12-hour clock hour.
`[hour repr:24]`	Output a 24-hour clock hour.
`[unix_timestamp precision:millisecond]`	Output Unix timestamp milliseconds.

Examples

Date:

[year]-[month]-[day]

Output:

2026-06-24

Timestamp with offset:

[year]-[month]-[day]T[hour]:[minute]:[second][offset_hour sign:mandatory]:[offset_minute]

Output:

2026-06-24T08:45:12+03:00

Filename-safe timestamp:

[year]-[month]-[day]T[hour]-[minute]-[second].[subsecond digits:3][offset_hour sign:mandatory][offset_minute]

Output:

2026-06-24T08-45-12.123+0300

Invalid field names or modifiers make the configuration invalid. Radiator validates timestamp_format() when it loads the pipeline. Radiator validates rotated-filename when it parses the file logger configuration.

Table of Contents

Timestamp Format
Date Fields
Time Fields
Offset Fields
Unix Timestamp Field
Common Modifiers
Examples
Error Handling

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