Power Platform Community Forum Thread Details

Hii

Im a beginner in Power Apps. I am building a weekly calendar for lecturers to see their weekly schedule in Power Apps using a vertical gallery.

I am using the following Power Fx formula to check if a session exists for a date:

!IsBlank(
LookUp(
Table1_1,
'Session Date' = DateAdd(_firstDayInView, ThisItem.Value, TimeUnit.Days)
)
)

The formula is supposed to check if there is a record for the session date.

However, I am getting an error when using it in my gallery.
My data source is an Excel table.

Can someone explain what might be wrong with this formula?

Thank you

Categories:

Building Power Apps

Hi @CU10030108-0,

The issue is almost certainly a date type mismatch. Excel stores dates as serial numbers, and Power Apps reads them as text or number, not as a native Date type. So comparing 'Session Date' directly to a DateAdd() result fails because the types don't match.

Try wrapping the column in DateValue() to force the conversion:

!IsBlank(
  LookUp(
    Table1_1,
    DateValue(Text('Session Date')) = DateAdd(_firstDayInView, ThisItem.Value, TimeUnit.Days)
  )
)

If the column comes through as a number (Excel serial), use this instead:

!IsBlank(
  LookUp(
    Table1_1,
    DateAdd(Date(1899,12,30), Value('Session Date'), TimeUnit.Days) = DateAdd(_firstDayInView, ThisItem.Value, TimeUnit.Days)
  )
)

A few things worth checking:

Column name spacing. 'Session Date' with a space requires the single-quote syntax. Confirm that the column name in your Excel table matches exactly, including the case.

Excel connection type. If you connected via "Excel Online (Business)," date columns sometimes come through differently than a static upload. Check the actual data type Power Apps infers by looking at the column in the Data panel.

Time components. If the 'Session Date' field stores a datetime that includes a time portion, the equality check will fail even when the dates appear visually identical. Wrap both sides in DateValue() to strip the time.

Thank you!
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