Cron next runs

cron-next-runs · version 1.0.0 · Other utilities · free, no key needed

Compute the next requested UTC fire times for a five-field cron schedule and echo the supplied reference instant.

Use when you need to: next cron runs · calculate upcoming cron fire times · when will this cron run next.

Decide before calling

Read the versioned contract and the supported scope below. Reuse cron-next-runs@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use cron-next-runs@1.0.0 for next cron runs. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• next cron runs
• calculate upcoming cron fire times
• when will this cron run next
• find future schedule executions
• cron times after an instant
• evaluate cron forward in UTC

Not supported

• six-field cron with seconds
• named months or weekdays
• IANA time zone daylight-saving rules

Behavior

• Vixie wildcard status is true when a field starts with *, including */n; if either day field starts with *, both day value sets must match; otherwise day matching uses OR.
• Uses POSIX.1-2024 crontab utility INPUT FILES section five-field ordering; two restricted day fields use OR matching.
• Supports Vixie cron 3.0pl1 list, inclusive range, and step extensions.
• Runs are strictly after reference_instant, returned as UTC minute instants; offset defaults to Z.
• The supplied reference_instant is echoed unchanged and the host clock is never read.

Input

• expression (string, required): min length 1; max length 128
• reference_instant (string, required): min length 20; max length 20; pattern ^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$
• count (integer, required): min 1; max 32
• offset (string, optional): min length 1; max length 6; pattern ^(Z|[+-]\d{2}:\d{2})$

Output

• expression (string, required): min length 1; max length 128
• reference_instant (string, required): min length 20; max length 20; pattern ^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$
• offset (string, required): min length 1; max length 6; pattern ^(Z|[+-]\d{2}:\d{2})$
• runs (array of string, required): min items 1; max items 32; each min length 20; each max length 20; each pattern ^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$
• standard_version (constant "POSIX.1-2024 crontab utility, INPUT FILES", required)

Limits

• max input bytes: 512
• max expression bytes: 128
• max results: 32
• max search minutes: 527040
• max output bytes: 4096

Example

Request input:

{
  "expression": "15 * * * *",
  "reference_instant": "2026-01-01T00:00:00Z",
  "count": 2
}

Response:

{
  "result": {
    "expression": "15 * * * *",
    "reference_instant": "2026-01-01T00:00:00Z",
    "offset": "Z",
    "runs": [
      "2026-01-01T00:15:00Z",
      "2026-01-01T01:15:00Z"
    ],
    "standard_version": "POSIX.1-2024 crontab utility, INPUT FILES"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "cron-next-runs",
  "version": "1.0.0",
  "input": {
    "expression": "15 * * * *",
    "reference_instant": "2026-01-01T00:00:00Z",
    "count": 2
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/cron-next-runs/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"expression":"15 * * * *","reference_instant":"2026-01-01T00:00:00Z","count":2}'

The machine-readable contract is at /v1/tools/cron-next-runs/versions/1.0.0.

CLI

node cli.mjs run cron-next-runs 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Cron previous runs: Compute the previous requested UTC fire times for a five-field cron schedule and echo the supplied reference instant.
• Base64url validate: Check canonical base64url syntax and return validity plus the first invalid character when present.
• Cron expression validate: Check whether a five-field cron expression is supported and return a validity flag with a reason code.
• Stats percentile: Compute an exact percentile from decimal strings using a named Hyndman-Fan type 1 through 9.
• Array duplicates find: List duplicated JSON values with counts and first indexes, preserving first-seen order.
• Array set difference: Return unique left-array values absent from the right array, in first-seen order.