GlideDateTime.getDayOfMonth()

gdt.getDayOfMonth()→ number

beginnerTested on Xanadu

What It Does

The getDayOfMonth() method extracts the day component from a GlideDateTime object and returns it as a numeric value between 1 and 31. The calculation is performed in UTC timezone, regardless of the user's session timezone or system timezone settings.

Internally, ServiceNow converts the GlideDateTime's internal millisecond timestamp to a UTC-based Calendar object, then extracts the DAY_OF_MONTH field. This means a datetime of '2024-03-15 23:30:00' will always return 15, even if the user's timezone would display it as the 16th.

The method returns a JavaScript number type, not a string. For invalid or null GlideDateTime objects, it returns NaN. The returned value will never be 0 or greater than 31, as it follows standard calendar month day numbering.

Edge cases include leap year February 29th (returns 29), and months with varying day counts. The method doesn't validate whether the day makes sense for the current month—it simply extracts whatever day component exists in the datetime object.

Related methods include getDayOfMonthLocalTime() which applies timezone conversion, getDayOfWeek() for weekday extraction, and getMonthUTC() for month values. All follow the same UTC-based calculation pattern.

When to Use This

Use getDayOfMonth() when building server-side logic that needs consistent day-of-month values regardless of user timezones. Common scenarios include automated scheduling based on monthly cycles, date range filtering in GlideRecord queries, and business rule conditions that trigger on specific calendar days.

When building user-facing functionality or reports where timezone matters to the user experience, use getDayOfMonthLocalTime() instead. Similarly, for client-side JavaScript, browser Date objects handle timezone conversion automatically.

Avoid using this method for display purposes or when comparing dates entered by users in different timezones. The UTC-based calculation can create confusing results where a user's '15th of the month' entry shows up in logic as the 14th or 16th.

Return Value

Returns a JavaScript number between 1 and 31 representing the day of the month in UTC timezone. The value is always an integer—no decimal places or string formatting are applied.

For invalid GlideDateTime objects or null values, the method returns NaN. Always check for this using isNaN() when the source datetime might be invalid. Direct numeric comparison with NaN always returns false due to JavaScript's NaN behavior.

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Platform Behavior & Side Effects

No database operations are performed—this is purely a calculation method that reads from the GlideDateTime object in memory
No Business Rules, ACLs, or notifications are triggered since this method only reads existing datetime data
Performance is very fast—minimal CPU overhead for the UTC calendar calculation with no caching needed
Behaves identically in before/after Business Rules, Script Includes, and Scheduled Jobs—no execution context dependencies
Does not respect user session settings or preferences—always uses system UTC timezone for calculation
Multiple calls on the same GlideDateTime object return identical results—the underlying datetime value is not modified
Thread-safe for concurrent execution in scheduled jobs or high-volume Business Rules

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Code Examples

Extract day from incident created datebasic

// Check if incident was created on a month-end day for special processing
var inc = new GlideRecord('incident');
inc.get('INC0000123');

// Get the day of month when this incident was created
var createdDay = inc.sys_created_on.getDayOfMonth();

// Month-end processing (days 28-31 cover all month endings)
if (createdDay >= 28) {
    gs.info('Incident created near month end: day ' + createdDay);
    // Trigger special month-end processing logic
    inc.u_month_end_flag = true;
    inc.update();
}

// Alternative: check for specific monthly cycle day
if (createdDay == 15) {
    // Mid-month created incidents get different SLA
    inc.business_duration = '480'; // 8 hours
}

Demonstrates extracting the day component for business logic that depends on when in the month something occurred. Note the UTC behavior means this ignores user timezones.

Monthly report date filteringintermediate

// Generate report for all requests created on the 1st of any month
var gr = new GlideRecord('sc_request');
gr.addQuery('sys_created_on', '>=', '2024-01-01');
gr.query();

var firstOfMonthRequests = [];

while (gr.next()) {
    var createdDay = gr.sys_created_on.getDayOfMonth();
    
    // Only include requests created on the 1st
    if (createdDay == 1) {
        firstOfMonthRequests.push({
            number: gr.number.toString(),
            created: gr.sys_created_on.toString(),
            day: createdDay
        });
    }
}

gs.info('Found ' + firstOfMonthRequests.length + ' requests created on 1st of month');
return firstOfMonthRequests;

Shows how to filter records based on the day component when querying can't handle the day extraction directly. Useful for reporting patterns based on calendar days.

The classic timezone mistakeadvanced

// WRONG: Comparing user input with UTC day extraction
function checkMaintenanceDay(userSelectedDate) {
    var userGdt = new GlideDateTime(userSelectedDate);
    var selectedDay = userGdt.getDayOfMonth(); // UTC day!
    
    // User in PST selects "15th" but gets 14 or 16 in UTC
    if (selectedDay == 15) {
        return 'Maintenance day selected'; // Wrong!
    }
}

// RIGHT: Use local time method for user-facing logic
function checkMaintenanceDayCorrect(userSelectedDate) {
    var userGdt = new GlideDateTime(userSelectedDate);
    var selectedDay = userGdt.getDayOfMonthLocalTime(); // User's timezone
    
    if (selectedDay == 15) {
        return 'Maintenance day selected'; // Correct!
    }
}

Classic error mixing UTC server logic with user timezone expectations. Always use getDayOfMonthLocalTime() when dealing with user-entered dates or display logic.

Gotchas

The method returns the day in UTC timezone, so a user's '15th of the month' selection might return 14 or 16 depending on timezone offset.

Returns NaN for invalid GlideDateTime objects, and NaN comparisons always return false in JavaScript—use isNaN() to check.

Leap year February 29th correctly returns 29, but the method doesn't validate if the day is valid for the current month context.

The return value is a number type, not a string, so direct concatenation without toString() can cause unexpected results in some contexts.

Multiple calls on the same GlideDateTime instance return identical values—the method doesn't modify the underlying datetime object.

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