Holiday calendars

Shoals has no holiday-calendar module of its own. A business calendar is a Std.Datetime.Business.BusinessCalendar, and the market calendars come from the Shoreleave package. A Shoals function that needs a calendar, such as the Business252 day count, a business-day tenor, a spot lag, or an adjusted schedule, takes a BusinessCalendar argument; pass the Shoreleave calendar whose market and observance rules match the transaction.

Chelis does not re-export an imported name, so import the calendar from its Shoreleave module directly:

import Std.Datetime (date)
import Std.Datetime.Business (Following, business_day_roll)
import Shoreleave.UsFederal (us_federal)

rolled = business_day_roll(us_federal(), date(2025i64, 7i64, 4i64), Following)
-- Monday 2025-07-07: 4 July is a US federal holiday

Which calendar to use

Market	Shoreleave calendar	Module	Published horizon
US federal government holidays and closures	us_federal()	Shoreleave.UsFederal	2021-2030
New York Stock Exchange	nyse()	Shoreleave.Nyse	2026-2028
US bond market	sifma()	Shoreleave.Sifma	2026-2027
London	england_and_wales()	Shoreleave.EnglandAndWales	2019-2028
Tokyo	japan_bank()	Shoreleave.JapanBank	1990-2027
Sydney	new_south_wales()	Shoreleave.NewSouthWales	2026-2027
Hong Kong	hong_kong()	Shoreleave.HongKong	2025-2027
Euro settlement	target()	Shoreleave.Target	2026-2028

Each calendar keeps its source's holiday data, weekmask, and finite horizon. A business-day query outside the horizon fails with a domain error, and the try_ form in Std.Datetime.Business returns None; no calendar answers for a year its data does not cover.

The calendars name their own markets. Japan Bank includes bank-only closures such as 2 January. New South Wales public holidays do not include an August bank holiday. Hong Kong has a Monday-to-Saturday business week. There is no Frankfurt exchange calendar: TARGET is the euro settlement calendar and stays open on German public holidays such as 3 October.

Shoreleave has no Federal Reserve or USD settlement calendar. us_federal() is the federal government's calendar: the legal holidays plus executive-order closures of federal agencies, such as 24 and 26 December 2025, when the Federal Reserve Banks and Fedwire stayed open. sifma() and nyse() are not substitutes either; both close on Good Friday, for example.

Extending a calendar past its published horizon

def us_federal_projected(until_year: i64) -> BusinessCalendar
def try_us_federal_projected(until_year: i64) -> Option[BusinessCalendar]

Every module has this pair, named after its calendar (nyse_projected, target_projected, and so on). The result keeps the published holidays and adds the dates the calendar's observance rules generate for each year after the published horizon, through 31 December of until_year. The horizon starts where the published one starts. Rules produce only the recurring holidays: a one-off closure such as a federal executive order is never projected.

until_year must end after the published horizon and must not exceed the last year the rules are stated for: 2099 for japan_bank, 9998 for the others. Outside that range <name>_projected fails with a domain error naming the bound, and try_<name>_projected returns None. For example, try_us_federal_projected(2029i64) returns None because the published calendar already runs to 2030, and us_federal_projected(2029i64) fails with:

us_federal_projected: domain: until_year 2029 does not extend the published horizon, which ends in 2030; use the published calendar

us_federal_projected(2035i64) reports 4 July 2035 as a holiday.