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Dynamics 365 Community / Forums / Small and medium business | Business Central, N... / how to troubleshoot: M...
Small and medium business | Business Central, N...
Suggested Answer

how to troubleshoot: MRP/MPS: "Error when calculating backward. Calendar is not available before 01.01.1980 for Machine Center xy"

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Posted on by benovic 350

i have a case where i geht this error message in production, when running MRP/MPS.

 "Error when calculating backward. Calendar is not available before 01.01.1980 for Machine Center xy"

we extended the calendar until 1980 to check, but it seems even this is not enough.

I re-checked all the machine center lead times, checked on th earticle card, in the ressource calendars and found nothing that would indicate why the MPS is planning 40 Years backwards for our orders.

IN order to find the error, it would be nice to be able to get more insight.

any tips on how i could see what lines create the very long backwards planning?

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  • Suggested answer
    MahGah Profile Picture
    MahGah 15,613 on at

    Hi

    For machine center xy what is the UOM, Capacity , and Efficiency? Also, can you see a big production order?

    My guess is you have one big production order and when system uses the machine center / calendar setup and goes backward to set the start date it needs to go way back to calculate correct start date.

    Let say you want to make 1000 of one item and your capacity for machine center set to month and then uses 6 months then system needs to go back 500 years as a staring point.

    But I could be wrong here as well.

    I hope Ben Baxter  can provide a better explanation. 

  • Suggested answer
    Ben Baxter Profile Picture
    Ben Baxter 7,068 Super User 2026 Season 1 on at

    MahGah is spot on.  When creating/refreshing the Production Order the system is trying to calculate the start date.  This means it is taking the quantity times the run time of the routing lines to calculate the start time of each routing step.  The issue might not be Machine Center xy, but rather another operation happening prior that is pushing xy to start in the past.

    Check your Capacity Units of Measure on your Run Times for the Routing, which could be different than the machine card.  Then look at the calendar capacity for your machines.  Make sure the machines have availability to complete the operation(s) within a reasonable timeframe.

    This is most likely a mistaken Routing entry, such as 1000 minutes instead of .1000 minutes, which makes a huge difference in capacity requirements.

    Let us know what you find.

    Best Regards,

    Ben Baxter

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