At Job Scheduler Calculator
Calculate the execution time and countdown for a one-time 'at' scheduled job.
Inputs
Job Execution Time
2026-08-10 08:44:57 UTC
Time Until Execution
1h 30m
Equivalent at Command
at now + 90 minutes
Total Minutes Until Execution
90.0
Step by step
Values used
Delay Amount = 90; Delay Unit = Minutes
Execution time
execution_time = current_time + delay_amount × unit_to_ms_multiplier
Job Execution Time
= 2026-08-10 08:44:57 UTC
Time Until Execution
= 1h 30m
Equivalent at Command
= at now + 90 minutes
Total Minutes Until Execution
= 90.0
How it works
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)
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.