calculateLeadTime — GTM Variable Template for Date

VARIABLES › DATE

calculateLeadTime EXTENDED Date

Direct (.tpl) Apply (.tpl) Add to GTM

Calculates the lead time (in days) between the current date and the provided target date.

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When to Use This

Formatting

Normalize casing, spacing, encoding, and presentation of data values.

Date & Time

Calculate durations, differences, and time-based operations on date values.

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Examples

Future Date

INPUT

Target Date: 2024-04-25

OUTPUT

1

Today

INPUT

Target Date: 2024-04-24

OUTPUT

0

Past Date

INPUT

Target Date: 2024-04-23

OUTPUT

-1

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GTM Configuration

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Read-only Preview

calculateLeadTime

Target Date

▶️ Target date in YYYY-MM-DD format.

Supported formats:
  ✓ String

Input Setup

Input Function (optional)

⚙️ Optional pre-processing function applied to the input before internal logic (e.g., convert object to string, normalize case). Internal transformations such as case handling will still apply afterward.

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the result before returning it (e.g., str => str + ' €', val => val !== undefined for boolean conversion). Useful for chaining transformations on the output.

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Related Variables

Same category: Date

→ addDays → basicDateToExtended → calculateDaysDifference → currentTimestamp → dateToUnixTimestamp → daysToMilliseconds → extendedDateToBasic → getDayIndexFromDateString → getDayName → getDayNameFromDateString → getDayNameShort → getHourOfDay → getMonthName → getMonthNameShort → hoursToMilliseconds → isBusinessHours → isWeekend → millisecondsToDays → millisecondsToHours → millisecondsToMinutes → millisecondsToSeconds → minutesToMilliseconds → reverseDateCompactDay1st → reverseDateCompactYear1st → reverseDateSlash → secondsToMilliseconds → subtractDays → timestampToDayIndex → unixTimestampToDate

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Under the Hood

📜 View Implementation Code

/**
* Calculates the number of days between today and a future target date.
*
* @param {string} data.src - Target date in YYYY-MM-DD format.
* @param {Function|string} [data.out] - Optional output handler.
*
* Direct-mode specific parameters:
* @param {Function} [data.pre] - Optional pre-processor function.
*
* @returns {number|undefined} The lead time in days (positive if target date is in the future), or undefined if input is invalid.
*
* @framework ggLowCodeGTMKit
*/
const makeNumber = require('makeNumber');
const getTimestampMillis = require('getTimestampMillis');
const Math = require('Math');

const calculateLeadTime = function(targetDate) {
   if (typeof targetDate !== 'string') { return undefined; }
   const reDateFormatISO8601 = "^(\\d{4})-(\\d{2})-(\\d{2})$";
   const matchParts = targetDate.match(reDateFormatISO8601);
   if (matchParts === null) { return undefined; }

   function calculateDaysSinceEpoch(year, month, day) {
       function isLeapYear(year) {
           return (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0);
       }

       const daysInFebruary = isLeapYear(year) ? 29 : 28;
       const daysInMonth = [0, 31, daysInFebruary, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

       if (day > daysInMonth[month]) { return undefined; }

       let totalDays = 0;
       for (let y = 1970; y < year; y++) {
           totalDays += isLeapYear(y) ? 366 : 365;
       }
       for (let m = 1; m < month; m++) {
           totalDays += daysInMonth[m];
       }
       totalDays += day - 1;
       return totalDays;
   }

   const targetDays = calculateDaysSinceEpoch(makeNumber(matchParts[1]), makeNumber(matchParts[2]), makeNumber(matchParts[3]));
   if (targetDays === undefined) { return undefined; }

   const currentDays = Math.floor(getTimestampMillis() / (1000 * 60 * 60 * 24));

   return targetDays - currentDays;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// calculateLeadTime - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(calculateLeadTime(value));
// ===============================================================================
// calculateLeadTime() – Apply Mode
// ===============================================================================
/*
return function(value) {
   return out(calculateLeadTime(value));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Future Date'
✅ '[example] Today'
✅ '[example] Past Date'
✅ Invalid format returns undefined
✅ Invalid input - returns undefined