gc-fix-2657: split YEARFRAC parity change

docs/function-parity.md

@@ -1,6 +1,6 @@
 # Function parity: worksheet functions and formulas
 
-> **Last reviewed:** 2026-10-15 · **Last updated:** 2026-10-25 · **Change:** minor (the LAMBDA row lists the recursion limit and its `#NUM!`, and the error a defined name holding an error gives when called; earlier: number text with accounting parentheses coerces like Excel 365; INDEX with one index on a 2-D reference is #REF! as in Excel; earlier: SUBTOTAL and AGGREGATE cap the cells they visit, #2175) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-30 · **Last updated:** 2026-10-30 · **Change:** minor (function edge-case parity row; earlier: the LAMBDA row lists the recursion limit and its `#NUM!`, and the error a defined name holding an error gives when called; earlier: number text with accounting parentheses coerces like Excel 365; INDEX with one index on a 2-D reference is #REF! as in Excel; earlier: SUBTOTAL and AGGREGATE cap the cells they visit, #2175) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Excel's worksheet functions, category by category, against GridCraft's function library. Part of
 [target-app-parity.md](target-app-parity.md); gaps feed [gaps.md](gaps.md).
@@ -86,6 +86,7 @@ This improves series preparation; it does not change the model-fitting or season
 | Implicit intersection `@`, legacy CSE array formulas | done; legacy array range fill (PR #156) |
 | Implicit intersection `@`, legacy CSE array formulas | done, the entered range filled (PR #156) |
 | Array lifting: an array in a scalar argument evaluates the function per element | done. The Analysis ToolPak functions (EOMONTH, EDATE, WORKDAY(.INTL), NETWORKDAYS(.INTL), YEARFRAC, WEEKNUM, the COUP*, PRICE*, YIELD*, ODD*, TBILL*, ACCRINT*, AMOR*, DISC, DURATION, CUMIPMT/CUMPRINC, EFFECT, NOMINAL, DOLLARDE/FR, XNPV/XIRR rate and guess, FVSCHEDULE principal, ISEVEN/ISODD, QUOTIENT, MROUND, FACTDOUBLE, SQRTPI, RANDBETWEEN, SERIESSUM, the base conversions, CONVERT, DELTA, GESTEP, ERF/ERFC, BESSEL*, COMPLEX and IM* except IMSUM/IMPRODUCT) give `#VALUE!` for a reference to more than one cell in a value argument, as Excel 365 does in both dynamic-array and legacy formulas; array constants and computed arrays (`A1:A3+0`) still lift, and range arguments (holidays, schedule, cash flows) and the .INTL weekend accept ranges. Difference: BYROW/BYCOL pass their row or column to the LAMBDA as values, so `BYROW(A1:B3,LAMBDA(r,EOMONTH(r,0)))` lifts where Excel gives `#VALUE!` |
+| YEARFRAC basis 0, February-end start to day 31 | done: Excel 16.0 returns 31/360 for `YEARFRAC(2021-02-28,2021-03-31,0)` (0.08611111111111111); regression also covers leap day and reversed dates |
 | Trim references `A1:.E10` (trailing), `A1.:E10` (leading), `A1.:.E10` (both), also on whole rows/columns (`A:.A`) | done; evaluated as `TRIMRANGE(range, code, code)`, adjusted on insert/delete; files store `_xlfn.TRIMRANGE(range,code,code)` (Excel's own file spelling unconfirmed in public docs), `_xlfn._TRO_ALL/_TRO_LEADING/_TRO_TRAILING(...)` read too |
 | LET, LAMBDA, named LAMBDAs, ISOMITTED, MAP/REDUCE/SCAN/BYROW/BYCOL/MAKEARRAY | done. A LAMBDA that calls itself more than 140 times, or a formula nested past the depth limit, gives `#NUM!` (the target app allows deeper recursion, #1581). Calling a defined name that holds an error value gives that error, not `#NAME?` |
 | Iterative calculation for circular references | done: with Enable Iterative Calculation on (`formulas.calculationOptions` `{iterative, maxIterations, maxChange}`, saved as `<calcPr iterate iterateCount iterateDelta>`), loops are evaluated again from their previous values (blank = 0) until no cell on a loop changes by Maximum Change or Maximum Iterations is reached; off, cycles give `#CIRC!`. Set in File › Options › Formulas (Enable iterative calculation, Maximum Iterations 1 to 32767, Maximum Change 0 or more; the two fields are disabled while iteration is off). Differences: GridCraft recalculates on open, so a loop that never settles (`=A1+1`) advances again each time the file is opened
@@ -123,6 +124,7 @@ workbooks; results checked in as data, not Excel files) and fixing what it finds
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-30 | minor | Added a function edge-case parity row. |
 | 2026-10-25 | minor | LAMBDA row: a LAMBDA that calls itself more than 140 times, and a formula nested past the depth limit, give `#NUM!` (#1809; nesting gave `#CALC!` before). `=Foo(1)` where the defined name Foo holds `#N/A` gives `#N/A`, not `#NAME?` |
 | 2026-10-23 | minor | Number text coercion (VALUE, arithmetic, typed entry): a dollar sign before accounting parentheses (`$(1,234)`, `$ (5)`) and a percent sign after them (`(5)%`) read as negatives; `(-5)`, `((5))`, `($-5)`, `$5%`, `$(5)%` and dates or times in parentheses are `#VALUE!`, as observed in Excel 365 |
 | 2026-10-23 | minor | INDEX with only a row index on a reference of several rows and columns (`INDEX(A1:C3,2)`, `INDEX(A1:C3,0)`) is `#REF!`, as observed in Excel, so it also fails as a range endpoint and inside other functions; an empty column argument (`INDEX(A1:C3,2,)`) still gives the row. Checked that a column array with one index stays a 1×1 array (`TYPE` 64), which is what Excel returns |