Tenors

Module: Shoals.Tenor.

This module represents a tenor as a count and a unit, provides constructors for the common units including the overnight family, converts a tenor to a number of days, and advances a date by a tenor. Dates come from Std.Time.

Types

type TenorUnit =
  | Day
  | Week
  | Month
  | Year
  | Overnight
  | TomorrowNext
  | SpotNext

type Tenor =
  | Tenor { count: int64, unit: TenorUnit }

A Tenor is a count and a TenorUnit. The units include calendar steps (day, week, month, year) and the three overnight settlement steps: overnight, tomorrow-next, and spot-next.

Constructors

def tenor(count: int64, unit: TenorUnit) -> Tenor
def days_n(n: int64) -> Tenor
def weeks_n(n: int64) -> Tenor
def months_n(n: int64) -> Tenor
def years_n(n: int64) -> Tenor
def overnight() -> Tenor
def tomorrow_next() -> Tenor
def spot_next() -> Tenor

tenor is the general constructor; days_n, weeks_n, months_n, and years_n build a tenor of n of the corresponding unit; and overnight, tomorrow_next, and spot_next build the three settlement tenors. A negative count expresses a step into the past.

Conversion and application

def days_per_unit(unit: TenorUnit) -> int64
def tenor_to_days(t: Tenor) -> int64
def tenor_apply(t: Tenor, reference: Date) -> Date

days_per_unit returns the day count of a single unit: a day is one, a week seven, a month thirty, a year three hundred sixty-five, overnight one, tomorrow-next two, and spot-next three. tenor_to_days multiplies the count by the unit's day count. tenor_apply advances a reference date by the tenor's day count.

From tests/tenor.ch, three months is ninety days and advances a reference date by ninety days:

d = tenor_to_days(months_n(cast(3, int64)))  // d == 90

ref = date(cast(2025, int64), cast(6, int64), cast(15, int64))
shifted = tenor_apply(months_n(cast(3, int64)), ref)
// days_between(ref, shifted) == 90

Months and years use the fixed thirty-day and three-hundred-sixty-five-day approximations, so tenor arithmetic is calendar-day arithmetic, not calendar-aware month stepping. Parsing a tenor from a string is not part of this surface; see Scope and limitations.