Struct DaysFn 

pub struct DaysFn;

Returns the number of whole days between two date serial values.

Remarks

• Result is end_date - start_date; negative results are allowed.
• Fractional serial inputs are truncated to their date portion.
• Serials are interpreted with the Excel 1900 mapping (including the 1900 leap-year bug behavior).
• This function currently does not switch interpretation based on workbook 1900/1904 mode.

Examples

title: "Positive day difference"
formula: "=DAYS(45366, 45323)"
expected: 43

title: "Negative day difference"
formula: "=DAYS(45323, 45366)"
expected: -43

related:
  - DATEDIF
  - DAYS360
  - NETWORKDAYS
faq:
  - q: "Does DAYS count partial-day time fractions?"
    a: "No. DAYS truncates both serial inputs to whole dates before subtracting end_date - start_date."

Trait Implementations

impl Debug for DaysFn

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Function for DaysFn

[formualizer-docgen:schema:start] Name: DAYS Type: DaysFn Min args: 2 Max args: 2 Variadic: false Signature: DAYS(arg1: number@scalar, arg2: number@scalar) Arg schema: arg1{kinds=number,required=true,shape=scalar,by_ref=false,coercion=NumberLenientText,max=None,repeating=None,default=false}; arg2{kinds=number,required=true,shape=scalar,by_ref=false,coercion=NumberLenientText,max=None,repeating=None,default=false} Caps: PURE [formualizer-docgen:schema:end]

fn caps(&self) -> FnCaps

Capability flags for this function

fn name(&self) -> &'static str

fn min_args(&self) -> usize

fn arg_schema(&self) -> &'static [ArgSchema]

fn eval<'a, 'b, 'c>( &self, args: &'c [ArgumentHandle<'a, 'b>], _ctx: &dyn FunctionContext<'b>, ) -> Result<CalcValue<'b>, ExcelError>

The unified evaluation path.

fn namespace(&self) -> &'static str

fn variadic(&self) -> bool

fn volatile(&self) -> bool

fn aliases(&self) -> &'static [&'static str]

Optional list of additional alias names (case-insensitive) that should resolve to this function. Default: empty slice. Implementors can override to expose legacy names. Returned slice must have ’static lifetime (typically a static array reference).

fn function_salt(&self) -> u64

fn eval_reference<'a, 'b, 'c>( &self, _args: &'c [ArgumentHandle<'a, 'b>], _ctx: &dyn FunctionContext<'b>, ) -> Option<Result<ReferenceType, ExcelError>>

Optional reference result path. Only called by the interpreter/engine when the callsite expects a reference (e.g., range combinators, by-ref argument positions, or spill sources).

fn dispatch<'a, 'b, 'c>( &self, args: &'c [ArgumentHandle<'a, 'b>], ctx: &dyn FunctionContext<'b>, ) -> Result<CalcValue<'b>, ExcelError>

Dispatch to the unified evaluation path with automatic argument validation.