happytails.ai

Age Calculator

Open Age Calculator on Happytails.ai. This view has the same page content and links, with explicit tool capabilities. Read the processing notes before using a tool.

Tool capabilities

{
  "id": "age-calculator",
  "category": "date-time-tools",
  "built": true,
  "requirements": "Calendar age and next birthday; leap-day handling; dates stay local.",
  "implementation": {
    "fields": [
      {
        "key": "start",
        "label": "Start date",
        "value": "2026-01-01",
        "type": "date"
      },
      {
        "key": "end",
        "label": "End date",
        "value": "2026-12-31",
        "type": "date"
      },
      {
        "key": "holidays",
        "label": "Holidays to exclude (YYYY-MM-DD, comma separated)",
        "value": "",
        "type": "text"
      }
    ],
    "input": false,
    "experience": {
      "automatic": true,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Hello world!",
      "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
      "helpParts": [
        "Change the input or settings to update your result.",
        "Results update as you type.",
        "Up to 1,000,000 characters."
      ],
      "action": null
    },
    "mode": "automatic",
    "interactive": false
  },
  "execution": "POST /api/v1/tools/age-calculator/run",
  "api": {
    "id": "age-calculator",
    "name": "Age calculator",
    "category": "date-time-tools",
    "description": "Calendar age and next birthday.",
    "notes": "",
    "human_path": "/en/date-time-tools/age-calculator/",
    "method": "POST",
    "endpoint": "/api/v1/tools/age-calculator/run",
    "schema_url": "/api/v1/tools/age-calculator",
    "input_schema": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "input": {
          "type": "string",
          "maxLength": 1000000,
          "default": "",
          "description": "Plain text input. File tools use files instead unless otherwise documented."
        },
        "options": {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "start": {
              "type": "string",
              "description": "Start date",
              "default": "2026-01-01"
            },
            "end": {
              "type": "string",
              "description": "End date",
              "default": "2026-12-31"
            },
            "holidays": {
              "type": "string",
              "description": "Holidays to exclude (YYYY-MM-DD, comma separated)",
              "default": ""
            }
          }
        }
      }
    },
    "output_schema": {
      "type": "object",
      "required": [
        "tool",
        "result"
      ],
      "properties": {
        "tool": {
          "type": "string"
        },
        "result": {
          "type": "object",
          "required": [
            "text",
            "files"
          ],
          "properties": {
            "text": {
              "type": [
                "string",
                "null"
              ]
            },
            "data": {
              "description": "Parsed JSON when the textual result is JSON."
            },
            "name": {
              "type": "string"
            },
            "mime": {
              "type": "string"
            },
            "files": {
              "type": "array",
              "items": {
                "type": "object",
                "required": [
                  "name",
                  "mime",
                  "bytes",
                  "base64"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "mime": {
                    "type": "string"
                  },
                  "bytes": {
                    "type": "integer"
                  },
                  "base64": {
                    "type": "string",
                    "contentEncoding": "base64"
                  }
                }
              }
            }
          }
        }
      }
    },
    "processing": "Server; same transformation code as browser tools",
    "limits": {
      "request_bytes": 8388608,
      "input_characters": 1000000,
      "files_bytes": 5242880,
      "max_files": 0,
      "timeout_seconds": 12
    }
  },
  "agent_processing": "Server; same transformation code as browser tools",
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}

Page guide

Work out completed years and total days between two dates.

How to use Age calculator
  1. Enter the values you want to calculate and choose the relevant units or settings.
  2. The result updates as you type. Adjust the available settings if needed.
  3. Review the result, then use Copy result or a download link when available.

Useful next steps

Date differenceAdd daysBusiness days

How Age calculator works

Pick a birth date and an end date, and the age calculator returns your age in completed years plus the total number of days between the two dates. A year counts only once its anniversary has been reached, the same way people state their age. Dates use the YYYY-MM-DD format and are treated as whole calendar days, so time of day and time zones do not affect the result. It is calculated in your browser and does not show months or weeks.

Before you start

Enter the birth date as the start date and the date you want the age for, often today, as the end date. Both must be real calendar dates, and the end cannot come before the start.

A worked example

A birth date of 1990-05-15 and an end date of 2026-10-20 gives 36 completed years and 13,307 total days.

Continue your workflow: Date difference, Add days, Business days.

Common questions

How is age calculated in years?

Subtract the birth year from the end year, then take away one if the birthday has not yet occurred in the end year. Someone born on 1990-05-15 is 35 on 2026-05-14 and turns 36 on 2026-05-15. The calculator follows this completed-years rule.

What about someone born on February 29?

In years without February 29, this calculator counts the new year of age from March 1. For a birth date of 2000-02-29, the result on 2026-02-28 is 25 years, and on 2026-03-01 it is 26. Legal rules for leap-day birthdays vary by country, so check if it matters officially.

Can I calculate the age at a past or future date?

Yes. The end date does not have to be today. Set it to any date on or after the birth date, such as an application deadline or a retirement date. If the end date is earlier than the start date, the tool shows an error instead of a negative age.

Why is my date not accepted?

Dates must use the YYYY-MM-DD format, such as 1990-05-15. Formats like 05/15/1990 are rejected because they are ambiguous between countries. Impossible dates, such as 2023-02-29, are also refused, since 2023 was not a leap year.