now
This page explains how to use the now function in APL.
Use the now function in APL to return the current UTC clock time as a datetime value, optionally offset by a given timespan. now is evaluated once at the start of the query and returns the same fixed value for the entire duration of the query, regardless of how long the query takes to run. This means all uses of now within a query refer to the same point in time.
You can use now to calculate relative times, filter events by recency, and compute the age of records in your dataset.
Use it when you want to:
- Filter events to a recent time window.
- Calculate how long ago an event occurred.
- Add the current timestamp to query output for audit or comparison purposes.
Usage
Syntax
now([offset])Parameters
| Name | Type | Description |
|---|---|---|
| offset | timespan | Optional: A timespan added to the current UTC clock time. Default is 0. |
Returns
The current UTC clock time as a datetime. All references to now() within a single statement return the same value.
Use case examples
Calculate the age of each request in hours to understand how recent events are.
Query
['sample-http-logs']
| extend age_hours = datetime_diff('hour', now(), _time)
| project _time, age_hours, method, status
| take 10Output
| _time | age_hours | method | status |
|---|---|---|---|
| 2025-01-15T10:00:00Z | 48 | GET | 200 |
| 2025-01-15T10:05:00Z | 47 | POST | 201 |
| 2025-01-15T10:10:00Z | 47 | GET | 500 |
This query calculates how many hours ago each HTTP request occurred by comparing the event time to the current time.
Find traces from the last 5 minutes to monitor recent activity by service.
Query
['otel-demo-traces']
| where _time > now(-5m)
| summarize trace_count = count() by ['service.name']Output
| service.name | trace_count |
|---|---|
| frontend | 120 |
| cart | 85 |
| checkout | 42 |
This query filters traces to those generated in the last 5 minutes and counts them by service name.
Show the current time alongside each failed request to calculate how many minutes have passed since the event.
Query
['sample-http-logs']
| where toint(status) >= 400
| extend current_time = now()
| extend time_since = datetime_diff('minute', current_time, _time)
| project _time, current_time, time_since, status, uri
| take 10Output
| _time | current_time | time_since | status | uri |
|---|---|---|---|---|
| 2025-01-15T10:00:00Z | 2025-01-17T10:00:00Z | 2880 | 403 | /admin |
| 2025-01-15T10:05:00Z | 2025-01-17T10:00:00Z | 2875 | 500 | /api/users |
| 2025-01-15T10:10:00Z | 2025-01-17T10:00:00Z | 2870 | 404 | /missing |
This query adds the current timestamp to each record and calculates the elapsed time in minutes since each failed request occurred.
List of related functions
- ago: Subtracts a given timespan from the current UTC clock time.
- datetime_add: Adds a specified amount to a datetime value.
- datetime_diff: Calculates the difference between two datetime values.
- startofday: Returns the start of the day for a datetime value.
- endofday: Returns the end of the day for a datetime value.