timestampToDayIndex — GTM Variable Template for Date
timestampToDayIndex EXTENDED Date
Converts a Unix timestamp in milliseconds to a day index since epoch. Useful for measuring days between events.
When to Use This
Date Formatting
Format and transform date values into human-readable or machine-readable strings.
Type Conversion
Safely convert between data types — strings, numbers, booleans, arrays, objects.
Date & Time
Calculate durations, differences, and time-based operations on date values.
Examples
Convert timestamp to day index
INPUT
Timestamp: 1718726400000
OUTPUT
19892
Invalid input returns undefined
INPUT
Timestamp: invalid
OUTPUT
undefined
GTM Configuration
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timestampToDayIndex
Timestamp
💾 The Unix timestamp in milliseconds to convert to a day index.
Supported formats:
✓ Number: 1718726400000
✓ Stringified Number: "1718726400000"
✓ Variable: {{currentTimestamp}}
Supported formats:
✓ Number: 1718726400000
✓ Stringified Number: "1718726400000"
✓ Variable: {{currentTimestamp}}
Input Setup
Input Function (optional)
⚙️ Optional pre-processing function applied to the input before internal logic (e.g., parse string to number, apply mathematical operations). Internal transformations such as absolute value calculation will still apply afterward.
Result Handling
Output Function (optional)
⚙️ Optional function to apply to the day index before returning it (e.g.,
x => x * -1 to negate, x => x.toString() to convert to string).Timestamp number
💡 Type any text to see the result update live
🎯 Using special value — click input to type instead
Test with:
Falsy
Truthy
🔗 Result Handling — Chain Variables
Chain apply-mode variables to the output. Each variable receives the result of the previous one.
timestampToDayIndex()
Related Variables
Same category: Date
Under the Hood
📜 View Implementation Code
/**
* Converts a Unix timestamp in milliseconds to a day index since epoch (January 1, 1970).
* Useful for calculating the number of days between two events by subtracting day indices.
*
* @param {number} data.src - The Unix timestamp in milliseconds.
* @param {Function|string} [data.out] - Optional output handler.
*
* Direct-mode specific parameters:
* @param {Function} [data.pre] - Optional pre-processor function.
*
* @returns {number} The day index since epoch, or undefined if input is invalid.
*
* @framework ggLowCodeGTMKit
*/
const makeNumber = require('makeNumber');
const Math = require('Math');
const timestampToDayIndex = function(timestamp) {
const ts = makeNumber(timestamp);
if (typeof ts !== 'number' || ts !== ts) return undefined;
return Math.floor(ts / 86400000);
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// timestampToDayIndex - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(timestampToDayIndex(value));
// ===============================================================================
// timestampToDayIndex(...) – Apply Mode
// ===============================================================================
/*
return function(timestamp) {
return out(timestampToDayIndex(timestamp));
};
*/🧪 View Test Scenarios (5 tests)
✅ '[example] Convert timestamp to day index'
✅ Difference between two day indices equals number of days
✅ Same day returns same index
✅ Stringified number is converted
✅ '[example] Invalid input returns undefined'