ISO date range split by month

iso-date-range-split-by-month · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Split an inclusive [start, end] date range into per-calendar-month sub-ranges.

Use when you need to: iso date range split by month · chunk date range by calendar month · monthly billing periods from range.

Supported

iso date range split by month
chunk date range by calendar month
monthly billing periods from range

Not supported

fiscal months
split by week or quarter
timezones

Behavior

start and end are strict YYYY-MM-DD calendar dates with year 0001-9999. start must not be after end.
The range is split into at most 1200 consecutive sub-ranges, one per calendar month it touches.
The first sub-range starts at start (not necessarily the 1st). The last sub-range ends at end (not necessarily the month end). Every sub-range in between spans a full calendar month.
Sub-ranges are contiguous and in ascending order; their union covers exactly [start, end] with no gaps or overlaps.

Input

start (string, required): min length 10; max length 10; pattern ^\d{4}-\d{2}-\d{2}$
end (string, required): min length 10; max length 10; pattern ^\d{4}-\d{2}-\d{2}$

Output

ranges (array of object, required)

Limits

year min: 1
year max: 9999
max segments: 1200

Example

Request input:

{
  "start": "2026-01-20",
  "end": "2026-03-10"
}

Response:

{
  "result": {
    "ranges": [
      {
        "start": "2026-01-20",
        "end": "2026-01-31"
      },
      {
        "start": "2026-02-01",
        "end": "2026-02-28"
      },
      {
        "start": "2026-03-01",
        "end": "2026-03-10"
      }
    ]
  }
}

How to call it

MCP

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

{
  "id": "iso-date-range-split-by-month",
  "version": "1.0.0",
  "input": {
    "start": "2026-01-20",
    "end": "2026-03-10"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-date-range-split-by-month/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"start":"2026-01-20","end":"2026-03-10"}'

The machine-readable contract is at /v1/tools/iso-date-range-split-by-month/versions/1.0.0.

CLI

node cli.mjs run iso-date-range-split-by-month 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

ISO date add months: Add a signed month count to a YYYY-MM-DD date, clamping the day to the target month.
ISO date add years: Add a signed whole-year delta to a YYYY-MM-DD date, clamping the day if 29 February has no match.
ISO date days in month: Return the number of calendar days in a given proleptic Gregorian year and month.
ISO date month end: Return the last valid calendar day of the year-month of a YYYY-MM-DD date.
ISO date month start: Return the first calendar day of the year-month of a YYYY-MM-DD date.
ISO date range union: Merge overlapping or day-adjacent inclusive [start, end] date ranges into the fewest equivalent ranges.