TBILLEQ Function (OpenOffice Calc)

• Introduced: First release not established; documented by OpenOffice.org 3.3.
• Supported in: Apache OpenOffice 4.1.16; this is a verified release, not a final supported version.
• Scope: Desktop Calc, English function names and semicolon-separated formulas.
• Checked: October 14, 2026. Eight ordinary reference formulas were recalculated from generated ODF in 4.1.16 on Linux x86-64, Build 9816. Source and independent arithmetic were checked.

TBILLEQ converts a discount rate using 365*Discount/(360-Discount*Days). This release obtains Days by adding one calendar day to Maturity and then applying its US 30/360 helper. That implementation detail must be checked against the convention required for a real security. Release implementation.

TBILLEQ(Settlement;Maturity;Discount)

• Settlement, Maturity: ordinary date serials, with a later maturity for the recommended use.
• Discount: positive annual discount rate as a decimal, such as 0.05.
• There is no optional Basis argument. Use a positive denominator and a supported short-term interval.

The native column contains saved 4.1.16 results; independent references use high-precision arithmetic and the stated source rules. Values are shown to twelve decimal places where needed. Enter DATE expressions directly rather than locale-dependent date text.

For January 1 to April 1, 2024 and a 5% discount rate, the release uses an adjusted count of 91. The result is 18.25/(360-0.05*91), approximately 0.051343367562, or 5.1343367562%.

For January 1 to July 1, it uses 181 rather than the actual 182 calendar days, producing approximately 0.052001709645. This is a concrete reason not to equate the native function’s result with an actual-day market calculation without checking the convention.

The order of adjustments matters. January 1 to January 31 first becomes a February 1 endpoint, giving a US 30/360 count of 30. Merely taking the original adjusted difference and adding 1 would give 31. The function follows the former sequence.

TBILLYIELD uses another sequence: it obtains the original date difference and then adds 1. TBILLPRICE also advances maturity first, but uses a year-fraction helper. Related names therefore do not guarantee interchangeable day-count calculations. When comparing yields, distinguish the supplied discount rate from the returned ratio and identify the intended denominator.

The source checks positive Discount, its adjusted settlement/maturity relation and a count no greater than 360, then requires a finite result. For practical use, validate Settlement<Maturity and 360-Discount*Days>0; the native examples all satisfy those ordinary conditions.

No same-day, reversed-date, excessive-rate or invalid-domain case was executed. The article reports release-specific calculation behavior, not a universal Treasury-bill pricing rule. If the required instrument convention uses actual days, calculate and verify that convention explicitly rather than silently substituting this helper’s count.

TBILLPRICE, TBILLYIELD, DISC.

• Function-specific release implementation
• US 30/360 adjustment helper

The generated ODF produced the informational load warning “Not all attributes could be read.” The sheet was hard-recalculated and saved separately. All eight ordinary function identities, inputs and results were reconciled; a stale SUM cache changed from 999999 to 3 and an uncached SUM returned 7. This establishes the stated examples, not every workbook style or invalid input. Other explanatory identities are independent calculations. The authoring-tool XLSX was not executed in OpenOffice, and its preview values are not the native results reported here.