Time Unit Converter in Excel

From To

30.43684939

Add-in Formula =PO.UnitConverter(1, "mo", "d")

Excel Lambda

=LAMBDA(x,
  LET(
    ratio, 30.4368493875386,
    x * ratio
  )
)(1)

Category Lambda

=LAMBDA(x, from, to,
  LET(
    f, SWITCH(from,
      "ms", 0.001,
      "s", 1,
      "min", 60,
      "h", 3600,
      "d", 86400,
      "wk", 604800,
      "mo", 2629743.78708333,
      "y", 31556925.445),
    t, SWITCH(to,
      "ms", 0.001,
      "s", 1,
      "min", 60,
      "h", 3600,
      "d", 86400,
      "wk", 604800,
      "mo", 2629743.78708333,
      "y", 31556925.445),
    x * f / t
  )
)(1, "mo", "d")

How to save as a reusable Excel function

LAMBDA is a built-in Excel feature (Microsoft 365) that lets you create custom functions without VBA. The formulas above work as-is when pasted into a cell.

To save a LAMBDA as a reusable named function:

Go to Formulas → Name Manager → New
Enter a name, e.g. ConvertTime
In Refers to, paste the LAMBDA formula without the trailing invocation (...)
Click OK

Now use =ConvertTime(1, "mo", "d") anywhere in your workbook — no add-in required.

Conversion Factors (base: s)

Unit	Name	Factor
s	second	1
ms	millisecond	0.001
min	minute	60
h	hour	3600
d	day	86400
wk	week	604800
mo	average month in tropical-year	2629743.78708333
y	tropical-year	31556925.445