Guide
Calendar-based vs meter-based maintenance
Calendar-based maintenance is triggered by the passing of time: a task is due on a date, whether the equipment ran a lot or a little. Meter-based maintenance is triggered by measured use, such as operating hours, cycles or distance, so the task is due when a reading is reached. Both are ways to plan preventive work; which one applies to a piece of equipment depends on its manufacturer's instructions and your site's rules, and some equipment uses both.
Calendar-based maintenance
In calendar-based maintenance, each task has a due date and repeats after a set amount of time.
What it needs to work: a first due date, an interval, and somewhere to keep the dates where people will see them, such as a shared calendar. It does not need anyone to take readings, which makes it simple to start.
When it falls short: when use varies a lot. A machine that sits idle for weeks reaches its due date with little wear, while one that runs around the clock may need attention well before the date comes. Calendar dates also say nothing about how the work went; they only say when it was planned.
Meter-based maintenance
In meter-based maintenance, a task is due when a usage reading reaches a set value since the last time it was done.
What it needs to work: a meter or counter on the equipment, someone who reads it regularly, and a record of each reading with its date and unit. The plan is only as good as those readings.
When it falls short: when readings are not taken, are written down inconsistently, or mix units. If nobody records the meter, the plan quietly stops working, and there is no date in a calendar to remind anyone.
Fixed due dates vs dates based on completion
There is a second choice inside calendar-based planning: where the next date is counted from.
- Fixed due dates. Every date is set in advance from the first due date. If the work is done late, the next due date does not move. This keeps a steady rhythm and makes late work easy to see.
- Dates based on completion. The next due date is counted from the day the work was actually finished. If the work is done late, every following date shifts later too.
Neither is right for every case, and switching from one to the other changes all future dates, so it is worth choosing deliberately. The scheduler on this site only uses fixed due dates.
Common mistakes
- Dates nobody sees. A schedule kept in one person's spreadsheet is easy to forget. Put due dates where the whole team looks, such as a shared calendar.
- Readings without units or dates. "1,240" means little later. Write the unit and the date with every meter reading.
- Changing the counting rule quietly. Moving from fixed due dates to dates based on completion, or the other way round, shifts every future date. Decide it once and write it down.
- Treating a due date as proof of work. A date in a calendar shows what was planned. Record what was actually done, by whom and when, in a work order or a maintenance log.
- One plan for very different machines. Two units of the same model can be used very differently. Check whether the manufacturer's instructions depend on use before copying a plan from one to the other.
Which one applies to your equipment
Start with the manufacturer's manual. It may give a time-based instruction, a usage-based one, or both with a rule such as "whichever comes first". Your site may add its own requirements, and regulated equipment may have rules of its own that a general guide cannot cover.
This guide does not suggest intervals for any machine. Take them from the manual and from people qualified to judge your equipment and how it is used.
Example schedule
Example — sample data. This is the example the preventive maintenance scheduler documents: a task first due on January 31, 2027, repeating every month, shown for 12 months. The monthly interval only illustrates how fixed due dates work; it is not a recommendation.
| # | Due date | Day |
|---|---|---|
| 1 | 2027-01-31 | Sun |
| 2 | 2027-02-28 | Sun |
| 3 | 2027-03-31 | Wed |
| 4 | 2027-04-30 | Fri |
| 5 | 2027-05-31 | Mon |
| 6 | 2027-06-30 | Wed |
| 7 | 2027-07-31 | Sat |
| 8 | 2027-08-31 | Tue |
| 9 | 2027-09-30 | Thu |
| 10 | 2027-10-31 | Sun |
| 11 | 2027-11-30 | Tue |
| 12 | 2027-12-31 | Fri |
| 13 | 2028-01-31 | Mon |
Notice how the 31st is handled. February, April, June, September and November have no 31st, so the task falls on the last day of those months, and the following month goes back to the 31st. Each date is counted from the first due date, so the schedule never drifts to the 28th for the rest of the year.
What this site covers
The preventive maintenance scheduler handles calendar-based tasks with fixed due dates and exports them to your calendar. It does not track meter readings, schedule from completion dates, or send reminders by itself. If your equipment is maintained by usage, keep the readings in the equipment maintenance log observations, and plan from them with your team.
Build a schedule
Use the free preventive maintenance scheduler to list the next due dates for a task and add them to your calendar.