In Prefect 3.x, you can set the Cron schedule’s

day_or

flag in

prefect.yaml

by adding

day_or: false

to the schedule entry. That turns “Day OR” OFF (i.e., requires both day-of-month and day-of-week to match when both are specified). Example

prefect.yaml

snippet:

deployments:
  - name: my-deployment
    entrypoint: flows/my_flow.py:my_flow
    work_pool:
      name: my-pool
    schedules:
      - slug: monthly-or-monday-9am-and
        cron: "0 9 1 * MON"   # 9:00 on the 1st of the month AND Monday
        timezone: "UTC"
        day_or: false         # Turn OFF "day OR" behavior (use AND)
        active: true

Notes: -

day_or: false

only changes behavior if both the day-of-month and day-of-week fields are constrained (not

*

). For example, with

cron: "0 9 * * MON"

,

day_or

has no effect since day-of-month is

*

. - Valid keys for a Cron schedule in

prefect.yaml

include:

cron

,

timezone

,

day_or

,

active

,

parameters

, and

slug

. Docs for reference: Prefect 3.x schedules