at Job Scheduler Calculator
Calculate the exact execution time for a one-off job scheduled with the at command.
About at Job Scheduler Calculator
The `at` command schedules a one-time job for a future point in time (unlike cron's recurring schedule), queued and executed by the atd daemon once the specified time arrives — the job runs exactly once and is then removed from the queue. This calculator converts a relative delay (e.g. '90 minutes from now') into the absolute wall-clock execution time and a human-readable countdown, along with the equivalent `at` command syntax you'd actually run.
Formula
Execution time
execution_time = current_time + delay_amount × unit_to_ms_multiplier
- T_{now}
- current time
- "\\Delta"
- delay amount
- m
- unit multiplier (ms per minute/hour/day)
Worked example
With the default values below, at Job Scheduler Calculator returns Job Execution Time of 2026-10-29 05:44:00 UTC. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Delay Amountminimum 0
- 90
- Delay Unitone of Minutes, Hours, Days
- Minutes
Results
- Job Execution Time
- 2026-10-29 05:44:00 UTC
- Time Until Execution
- 1h 30m
- Equivalent at Command
- at now + 90 minutes
- Total Minutes Until Execution
- 90.0
Step by step
- 1Values used
- 2Execution time
- 3Job Execution Time= 2026-10-29 05:44:00 UTC
- 4Time Until Execution= 1h 30m
- 5Equivalent at Command= at now + 90 minutes
- 6Total Minutes Until Execution= 90.0
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What's the difference between `at` and cron for scheduling?
cron is for recurring schedules (run every day at 2am, every 15 minutes, etc.), defined declaratively via a cron expression. `at` is for one-off, single-execution jobs scheduled relative to or at an absolute future time — after it runs once, the job is gone, unlike a crontab entry which persists and fires repeatedly.
Does the atd daemon need to be running for `at` jobs to execute?
Yes — `at` merely queues the job (typically under /var/spool/at/); the atd daemon must be running and polling that queue to actually execute jobs when their time arrives. On many distros atd is enabled by default, but it's worth confirming with `systemctl status atd` if a scheduled job doesn't run.
Can I list or cancel pending `at` jobs?
Yes — `atq` lists all pending jobs with their job number and scheduled time, and `atrm <job_number>` cancels a specific pending job before it executes.