Cron expression for the last day of the month — full guide

POSIX crontab has no last-day token, so you simulate it by enumerating the actual last day of each month. There are three groups: 30-day months, 31-day months, and February.

# 30-day months: April, June, September, November
0 0 30 4,6,9,11 * /path/to/script.sh

# 31-day months
0 0 31 1,3,5,7,8,10,12 * /path/to/script.sh

# February (leap-year safe — fires both 28th and 29th in leap years)
0 0 28,29 2 * /path/to/script.sh

The leap-year line is the trickiest. In non-leap years, only the 28th exists, so the cron fires once. In leap years, both the 28th and 29th exist; cron fires on both. To fire only on the actual last day, gate the script:

0 0 28,29 2 * [ "$(date -d tomorrow +%d)" = "01" ] && /path/to/script.sh

The wrapper checks “is tomorrow the 1st?”. Only on the actual last day of February (28th in non-leap, 29th in leap) is the answer yes.

Schedulers with extended cron support (Quartz, AWS EventBridge, robfig/cron, ncrontab, dragonmantank/cron-expression and several others) accept L in the day-of-month field. L auto-resolves to the last day of the current month — 28 / 29 / 30 / 31 — without you enumerating anything.

# Quartz / AWS EventBridge: midnight on the last day of every month
0 0 L * *           (Quartz 6-field, but Quartz needs ?)
0 0 0 L * ?         (Quartz 6-field with seconds and ? in day-of-week)
cron(0 0 L * ? *)   (AWS EventBridge)
0 0 L * *           (robfig/cron with cron.WithLocation)

The exact form differs per implementation. Quartz forbids both day-of-month and day-of-week being values, so one of them must be ?. AWS EventBridge has the same rule and additionally requires a year field. The dedicated guides for each library cover the platform-specific syntax in detail.

• Last day at midnight — 0 0 L * * or the multi-cron triplet above.
• Last weekday of the month — Quartz only: 0 0 0 LW * ?. Useful for monthly accounting that must run on a business day.
• Last Friday of the month — Quartz: 0 0 12 ? * 6L (1=Sunday, so 6=Friday).
• First and last day of the month — list: 0 0 1,L * * (where L is supported), or two separate cron lines.
• Two days before the last day — Quartz: 0 0 0 L-2 * ?. Other dialects don't accept arithmetic on L.

Bash / crontab

# Run nightly, exit unless tomorrow is the 1st.
0 0 28-31 * * [ "$(date -d tomorrow +%d)" = "01" ] && /path/to/script.sh

Java (Quartz)

Trigger trigger = TriggerBuilder.newTrigger()
    .withIdentity("monthEndTrigger")
    .withSchedule(CronScheduleBuilder.cronSchedule("0 0 0 L * ?"))
    .build();

Go (robfig/cron)

c := cron.New(cron.WithParser(cron.NewParser(
    cron.SecondOptional | cron.Minute | cron.Hour |
    cron.Dom | cron.Month | cron.Dow | cron.Descriptor)))
c.AddFunc("0 0 L * *", monthEndJob)
c.Start()

PHP (dragonmantank/cron-expression)

use Cron\CronExpression;
$cron = new CronExpression('0 0 L * *');
$next = $cron->getNextRunDate(); // DateTime of last day of month at midnight

AWS CloudFormation

Resources:
  MonthEndRule:
    Type: AWS::Events::Rule
    Properties:
      ScheduleExpression: "cron(0 0 L * ? *)"
      Targets:
        - Arn: !GetAtt MonthEndLambda.Arn
          Id: MonthEndLambdaTarget