Convert timestamps/dates across timezones

What it does

Convert timestamps/dates across timezones, execute relative date math, parse Unix timestamps, and calculate date differences

Request

Body

Field	Type	Required	Description
`add`	object	no	Relative duration to add to the date
`↳ days`	integer	no
`↳ hours`	integer	no
`↳ minutes`	integer	no
`↳ months`	integer	no
`↳ seconds`	integer	no
`↳ years`	integer	no
`compareDate`	string \| number	no	Optional secondary date to calculate difference/delta against primary date.
`date`	string \| number	no	ISO 8601 string, readable date, or Unix timestamp (seconds/ms). Omit for current server time.
`subtract`	object	no	Relative duration to subtract from the date
`↳ days`	integer	no
`↳ hours`	integer	no
`↳ minutes`	integer	no
`↳ months`	integer	no
`↳ seconds`	integer	no
`↳ years`	integer	no
`targetTimezone`	string	no	Valid IANA timezone identifier (e.g., "America/New_York", "Europe/London", "Asia/Tokyo", "UTC")

Example request

{
  "add": {
    "days": 20,
    "hours": 4,
    "minutes": 26,
    "months": 31,
    "seconds": 12,
    "years": 8
  },
  "compareDate": "2026-09-08",
  "date": "2026-09-08",
  "subtract": {
    "days": 20,
    "hours": 4,
    "minutes": 26,
    "months": 31,
    "seconds": 12,
    "years": 8
  },
  "targetTimezone": "UTC"
}

Response

Field	Type	Description
`components`	object
`↳ day`	integer
`↳ dayOfWeek`	integer
`↳ dayOfWeekName`	string
`↳ dayOfYear`	integer
`↳ hour`	integer
`↳ isLeapYear`	boolean
`↳ millisecond`	integer
`↳ minute`	integer
`↳ month`	integer
`↳ offset`	string
`↳ quarter`	string
`↳ second`	integer
`↳ weekOfYear`	integer
`↳ year`	integer
`difference`	object
`↳ breakdown`	object
`↳ diffMilliseconds`	number
`↳ humanized`	string
`↳ totalDays`	integer
`↳ totalHours`	integer
`↳ totalMinutes`	integer
`↳ totalSeconds`	integer
`formatted`	string
`iso`	string
`rfc2822`	string
`status`	string
`targetTimezone`	string
`tokensDeducted`	integer
`unixMilliseconds`	integer
`unixSeconds`	integer

Example response

{
  "components": {
    "day": 8,
    "dayOfWeek": 8,
    "dayOfWeekName": "Ada Lovelace",
    "dayOfYear": 2026,
    "hour": 31,
    "isLeapYear": true,
    "millisecond": 9,
    "minute": 33,
    "month": 9,
    "offset": "0",
    "quarter": "<quarter>",
    "second": 26,
    "weekOfYear": 2026,
    "year": 2026
  },
  "difference": {
    "breakdown": {
      "days": 20,
      "months": 31,
      "years": 8
    },
    "diffMilliseconds": 4.1,
    "humanized": "<humanized>",
    "totalDays": 3,
    "totalHours": 3,
    "totalMinutes": 3,
    "totalSeconds": 3
  },
  "formatted": "PL61 1090 1014 0000 0712 1981 2874",
  "iso": "<iso>",
  "rfc2822": "<rfc2822>",
  "status": "success",
  "targetTimezone": "Europe/Warsaw",
  "tokensDeducted": 1,
  "unixMilliseconds": 1,
  "unixSeconds": 22
}

Errors

Every error answers with the same envelope: an HTTP status, a machine code and a sentence.

`400`	The body or a parameter failed validation. The details array names the field.
`401`	No key, a revoked key or a wrong header. Send x-api-key.
`402`	The wallet cannot cover this call. Top up or wait for the monthly grant.
`404`	The resource does not exist, or it is not yours. Both answer identically and cost nothing.
`429`	Over the per-minute quota of your tier. Back off and retry.
`5xx`	Upstream refused or timed out. The call is not billed.

Code

curl -X POST 'https://app.castomapi.com/v1/convert/time' \
  -H 'x-api-key: <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{"add": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "compareDate": "2026-09-08", "date": "2026-09-08", "subtract": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "targetTimezone": "UTC"}'

const res = await fetch('https://app.castomapi.com/v1/convert/time', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"add": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "compareDate": "2026-09-08", "date": "2026-09-08", "subtract": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "targetTimezone": "UTC"})
});
const data = await res.json();
console.log(data);

import { request } from 'node:https';

// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/convert/time', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"add": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "compareDate": "2026-09-08", "date": "2026-09-08", "subtract": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "targetTimezone": "UTC"})
});
const data = await res.json();
console.log(data);

import requests

res = requests.post(
    'https://app.castomapi.com/v1/convert/time',
    headers={'x-api-key': '<your-api-key>'},
    json={"add": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "compareDate": "2026-09-08", "date": "2026-09-08", "subtract": {"days": 20, "hours": 4, "minutes": 26, "months": 31, "seconds": 12, "years": 8}, "targetTimezone": "UTC"},
    timeout=30,
)
print(res.json())

<?php
$ch = curl_init('https://app.castomapi.com/v1/convert/time');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
    CURLOPT_POSTFIELDS => json_encode(['add' => ['days' => 20, 'hours' => 4, 'minutes' => 26, 'months' => 31, 'seconds' => 12, 'years' => 8], 'compareDate' => '2026-09-08', 'date' => '2026-09-08', 'subtract' => ['days' => 20, 'hours' => 4, 'minutes' => 26, 'months' => 31, 'seconds' => 12, 'years' => 8], 'targetTimezone' => 'UTC']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);

Cost and limits

This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.

Rate limits per minute

No key	10
Free	60
Pro	300
Enterprise	1200

Docs → Pricing

Questions

What does Convert timestamps/dates across timezones cost?

This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.

How do I authenticate?

Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.

Can I send an Authorization: Bearer token instead?

Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.

What are the limits?

10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.

OpenAPI: https://app.castomapi.com/docs/json

Request

Response

What it does

Request

Body

Example request

Response

Example response

Errors

Code

Cost and limits

Rate limits per minute

Questions

More in Convert

Where it fits