> ## Documentation Index
> Fetch the complete documentation index at: https://docs.honeycomb.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Time Functions in Calculated Fields

> Time functions available for calculated field formulas in Honeycomb, including UNIX_TIMESTAMP, DATE_STRING, and duration helpers.

Time functions calculate and manipulate time data.

## `UNIX_TIMESTAMP`

Converts a date string in RFC3339 format (for example, `2017-07-20T11:22:44.888Z`) to a Unix timestamp (`1500549764.888`).
This is useful for comparing two timestamps in an event; for example, to calculate a duration from a start and an end timestamp.

```ruby theme={}
# Usage: UNIX_TIMESTAMP(string)
# Examples
UNIX_TIMESTAMP($timestamp)
```

## `EVENT_TIMESTAMP`

Returns the Unix timestamp, also known as the Epoch timestamp, of the current event as a float (`1500549764.888`, for example).
This is useful for comparing two timestamps in an event; for example, to calculate a duration from a start and an end timestamp.
This function takes no arguments.

```ruby theme={}
# Usage: EVENT_TIMESTAMP()
# Examples
EVENT_TIMESTAMP()
```

## `INGEST_TIMESTAMP`

Returns the Unix timestamp, also known as the Epoch timestamp, indicating when Honeycomb's servers received the current event, as a float (`1500549764.888`, for example).
This is useful for debugging event latency by comparing the event timestamp to the ingestion time.
This function takes no arguments.

```ruby theme={}
# Usage: INGEST_TIMESTAMP()
# Examples
# Event latency, in seconds. May be negative for future-dated events.
SUB(INGEST_TIMESTAMP(),EVENT_TIMESTAMP())
# Event latency, in minutes. May be negative for future-dated events.
DIV(SUB(INGEST_TIMESTAMP(),EVENT_TIMESTAMP()),60)
# Event latency, accounting for span duration. Assumes `duration_ms` is in milliseconds.
SUB(INGEST_TIMESTAMP(),SUM(EVENT_TIMESTAMP(),DIV($duration_ms,1000)))

```

## `FORMAT_TIME`

Formats a Unix timestamp, also known as an Epoch timestamp, as a string.
The first argument is a format specifier string compatible with [POSIX strftime](https://pubs.opengroup.org/onlinepubs/9699919799/functions/strftime.html), and the second argument is the numeric timestamp.
Does not support not-UTC timezones or locale-modified specifiers.
Also note this formatting is more expensive than other calculated field functions and may slow down queries, especially when using a complex format.

```ruby theme={}
# Usage: FORMAT_TIME(format, timestamp)
# Examples
FORMAT_TIME("%A", 1626810584)     # Tuesday
FORMAT_TIME("%FT%TZ", 1626810584) # 2021-07-20T19:49:44Z
```