NCRONTAB — last day of the month (Azure Functions)

using System;
using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;

public class MonthEndFunction
{
    [FunctionName("MonthEnd")]
    public void Run(
        [TimerTrigger("0 0 0 * * *")] TimerInfo myTimer,
        ILogger log)
    {
        var today = DateTime.UtcNow.Date;
        if (today.AddDays(1).Day != 1)
        {
            log.LogInformation("Not the last day of {Month} — skipping.", today.ToString("MMMM"));
            return;
        }

        log.LogInformation("Running month-end work for {Date}", today);
        // ... your last-day-of-month work here
    }
}

If you prefer to encode the “last day” logic in the schedule itself, register three timer triggers (one per month-length group):

[FunctionName("MonthEnd30")]
public void Run30([TimerTrigger("0 0 0 30 4,6,9,11 *")] TimerInfo t, ILogger log) => RunMonthEnd(log);

[FunctionName("MonthEnd31")]
public void Run31([TimerTrigger("0 0 0 31 1,3,5,7,8,10,12 *")] TimerInfo t, ILogger log) => RunMonthEnd(log);

[FunctionName("MonthEnd28")]
public void Run28([TimerTrigger("0 0 0 28 2 *")] TimerInfo t, ILogger log) {
    if (DateTime.UtcNow.AddDays(1).Day == 1) RunMonthEnd(log);
}

[FunctionName("MonthEnd29")]
public void Run29([TimerTrigger("0 0 0 29 2 *")] TimerInfo t, ILogger log) {
    if (DateTime.UtcNow.AddDays(1).Day == 1) RunMonthEnd(log);
}

Three or four functions for one logical job is a lot of boilerplate. The daily-with-runtime-check approach is usually cleaner.

• 6 fields — seconds, minute, hour, day-of-month, month, day-of-week.
• Always UTC in the consumption plan; the premium plan supports the WEBSITE_TIME_ZONE setting.
• No `L`, `W`, `?`, `#` — last-day, weekday, no-specific-value and Nth-weekday modifiers are unsupported.
• Step / list / range — supported in every field.
• Aliases — JAN-DEC, SUN-SAT accepted.

• Cold starts — Azure Functions on the consumption plan can take a few seconds to start. For a last-day-of-month job that needs to fire at exactly 00:00, use a Premium plan or the dedicated tier.
• Concurrent runs — by default, the timer trigger doesn't prevent overlap if the previous run is still going. Use a singleton lock if your work is not safe to run twice.
• Local development — `func host start` respects the cron schedule in real time. To test the runtime check, fake DateTime.UtcNow via a clock abstraction.