This script will extract the day, the month or the year from a date value for a range or specific cell. I also include a code for converting a month full name into a month number (for instance, January to 1).

 

When I use the script ?

When I have to perform different actions based only on the day, month or year (not the full date)

 

How to create the script ?

Read How to create, edit and select an Office Script in an excel report

 

How to create the button to associate it with the script ?

Read How to create a button and associated it to an Office Script in an excel report

 

How is/are the script(s) ?

Copy the code below and paste it into your script. You will see my comments in green if exist so follow the help to adapt to your need.

For one specific cell:

function main(workbook: ExcelScript.Workbook) {
    // change sheet1 by yours
    let sheet = workbook.getWorksheet("Sheet1");
    // change A2 by yours where it is the date
    let dnum = sheet.getRange("A2").getValue() as number;
    let dcvt = new Date((dnum - 25569) * 86400000);
    // for date, change getMonth() + 1 by getDate()
    // for year, change getMonth() + 1 by getFullYear()
    // for day, change getMonth() + 1 by getDay() - result = 1 is Monday and 7 is Sunday
    let dext = dcvt.getMonth() + 1;
    // change B2 by yours where to put the result
    // cell should be formatted as "general"
    sheet.getRange("B2").setValue(dext)
}              
              

For a range of cells:

function main(workbook: ExcelScript.Workbook) {
    // change sheet1 by yours
    let sheet = workbook.getWorksheet("Sheet1");
    // change A2:A10 by yours where it is the date column
    let dnum = sheet.getRange("A2:A10").getValues();
    // change B2:B10 by yours where to put the results
    let rngresult = sheet.getRange("B2:B10");
    let monthnum1: (number | string)[][] = [];
    let numvalue = dnum.map(row => {
        let date = row[0];
        return [typeof date === "number" ? date : new Date(date).getTime() / 86400000 + 25569];
    });
    numvalue.forEach((row) => {
        let serialDate = row[0];
        if (typeof serialDate === "number") {
            // for date, change getMonth() + 1 by getDate()
            // for year, change getMonth() + 1 by getFullYear()
            // for day, change getMonth() + 1 by getDay() - result = 1 is Monday and 7 is Sunday
            let monthnum2 = new Date((serialDate - 25569) * 86400000).getMonth() + 1;
            monthnum1.push([monthnum2]);
        }
    });
    rngresult.setValues(monthnum1);
}              
              

This code is to convert a month full name (for instance, January) into a month number (for instance, 1)

function main(workbook: ExcelScript.Workbook) {
    // change sheet1 by yours
    let sheetmi = workbook.getWorksheet("Sheet1");
    // change A2:A10 by yours where it is the full name month column
    let monname = sheetmi.getRange("A2:A10").getValues();
    // change B2:B10 by yours where to put the results
    let rngresult = sheetmi.getRange("B2:B10");
    for (let i = 0; i < monname.length; i++) {
        let cellval = monname[i][0];
        let monthNumber = getMonthNumber(cellval);
        if (monthNumber) {
            rngresult.getCell(i, 0).setValue(monthNumber);
        }
    }
}
function getMonthNumber(monthName: string): number | null {
    const months = ["January","February","March","April","May","June","July","August","September","October","November","December"];
    let monthIndex = months.findIndex(month => month.toLowerCase() === monthName.toLowerCase());
    return monthIndex !== -1 ? monthIndex + 1 : null;
}