Identify All Holiday Dates By Year using TSQL - sql-server

Question

I did a lot of searching for an easy solution to dynamically identify U.S. federal holidays by year. I wasn't able to find much information for the trickier holidays. Holidays like New Year's Day or Independence Day are easy to program as they are static. However, some are more difficult to identify programmatically such as Presidents' Day (3rd Monday in February) or Thanksgiving (4th Thursday in November).

Answer 1

I know this is an old question, but we have a sweet Scalar-valued Function that returns 1 if it's a holiday and 0 if it is not. We do have to manually add Observed Dates - We use the https://www.timeanddate.com/holidays/us/ to get the observed dates.
First, create the function:
USE [DATABASE]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[IsHoliday](#date as DATETIME)
RETURNS bit
AS
BEGIN
if #date is not null
begin
-- JAN
IF Month(#date)=1 AND day(#date)=1 return 1 -- New Years Day
IF Month(#date)=1 AND DATEPART(weekday, #date)=2 and day(#date)>14 and day(#date)<=21 return 1 -- Martin Luther King, Jr. Day
-- FEB
IF Month(#date)=2 AND DATEPART(weekday, #date)=1 and day(#date)<=7 return 1 -- Super Bowl Sunday
IF Month(#date)=2 AND day(#date)=14 return 1 -- Valentine's Day
IF Month(#date)=2 AND DATEPART(weekday, #date)=2 and day(#date)>14 and day(#date)<=21 return 1 -- Presidents' Day
-- MAR
IF Month(#date)=3 AND day(#date)=17 return 1 -- St Patrick's Day
-- MAY
IF Month(#date)=5 AND DATEPART(weekday, #date)=1 and day(#date)>7 and day(#date)<=14 return 1 -- Mother's day
IF Month(#date)=5 AND DATEPART(weekday, #date)=2 and day(#date)>24 and day(#date)<=31 return 1 --Memorial Day
-- JUN
IF Month(#date)=6 AND day(#date)=19 return 1 -- Juneteenth
IF Month(#date)=6 AND DATEPART(weekday, #date)=2 and day(#date)>14 and day(#date)<=21 return 1 --Father's Day
-- JUL
IF Month(#date)=7 AND day(#date)=4 return 1 -- July 4th
-- SEP
IF Month(#date)=9 AND DATEPART(weekday, #date)=2 and day(#date)<=7 return 1--Labor Day
-- OCT
IF Month(#date)=10 AND DATEPART(weekday, #date)=2 and day(#date)>7 and day(#date)<=14 return 1 --Columbus Day
IF Month(#date)=10 AND day(#date)=31 return 1 -- Halloween
-- NOV
IF Month(#date)=11 AND day(#date)=11 return 1 -- Veteran's Day
IF Month(#date)=11 AND DATEPART(weekday, #date)=5 and day(#date)>21 and day(#date)<=28 return 1 --Thanksgiving
-- DEC
IF Month(#date)=12 AND day(#date)=24 return 1 -- Christmas Eve
IF Month(#date)=12 AND day(#date)=25 return 1 -- Christmas Day
IF Month(#date)=12 AND day(#date)=31 return 1 -- NYE
-- Observed Dates
if month(#date)=1 AND day(#date)=2 AND year(#date)=2017 return 1 -- New Years Day observed for 2017
if month(#date)=11 AND day(#date)=10 AND year(#date)=2017 return 1 -- Veteran's Day observed for 2017
if month(#date)=11 AND day(#date)=12 AND year(#date)=2018 return 1 -- Veteran's Day observed for 2018
if month(#date)=7 AND day(#date)=3 AND year(#date)=2020 return 1 -- 4th of July Observed for 2021
if month(#date)=6 AND day(#date)=18 AND year(#date)=2021 return 1 -- Juneteenth observed for 2021
if month(#date)=7 AND day(#date)=5 AND year(#date)=2021 return 1 -- 4th of July Observed for 2021
if month(#date)=6 AND day(#date)=20 AND year(#date)=2022 return 1 -- Juneteenth observed for 2022
if month(#date)=12 AND day(#date)=26 AND year(#date)=2022 return 1 -- Christmas Day observed for 2022
if month(#date)=1 AND day(#date)=2 AND year(#date)=2023 return 1 -- New Years Day observed for 2023
if month(#date)=11 AND day(#date)=10 AND year(#date)=2023 return 1 -- Veteran's Day observed for 2023
if month(#date)=7 AND day(#date)=3 AND year(#date)=2026 return 1 -- 4th of July Observed for 2026
if month(#date)=6 AND day(#date)=18 AND year(#date)=2027 return 1 -- Juneteenth observed for 2027
if month(#date)=7 AND day(#date)=5 AND year(#date)=2027 return 1 -- 4th of July Observed for 2027
if month(#date)=11 AND day(#date)=10 AND year(#date)=2028 return 1 -- Veteran's Day observed for 2028
if month(#date)=11 AND day(#date)=12 AND year(#date)=2029 return 1 -- Veteran's Day observed for 2029
end
return 0
END
GO
Then call the function:
SELECT dbo.[IsHoliday](GETDATE())
SELECT dbo.[IsHoliday]('2021-07-05 09:20:51.270')

Answer 2

Here is the solution I came up with.
I created a table variable to store the entire years dates:
DECLARE #DateTable TABLE
(
dtDate DATE,
dtMonth VARCHAR(10),
dtDayName VARCHAR(10),
dtDayRank INT
);
Populated first 3 columns of the #DateTable:
DECLARE #Year CHAR(4), #CurrentDate DATE
SET #Year = '2018'
SET #CurrentDate = CAST(#Year + '0101' AS DATE)
WHILE #CurrentDate <= CAST(#Year + '1231' AS DATE)
BEGIN
INSERT INTO #DateTable (dtDate, dtMonth, dtDayName)
VALUES (#CurrentDate, DATENAME(mm, #CurrentDate), DATENAME(dw, #CurrentDate))
SET #CurrentDate = DATEADD(dd, 1, #CurrentDate)
END;
Once I had the table populated, I ranked the rows and updated the table:
UPDATE #DateTable
SET dtDayRank = rankdates.DayRank
FROM #DateTable datatable
INNER JOIN (
SELECT
dtDate,
DayRank = RANK() OVER (PARTITION BY dtMonth, dtDayName ORDER BY dtDate) -- rank each DayOfWeek in order
FROM #DateTable
) rankdates ON datatable.dtDate = rankdates.dtDate;
Sample Output from #DateTable
Once I had the #DateTable populated, I could use logic to identify specific days.
SELECT
HolidayName = 'Presidents'' Day',
ObservedDayOfWeek = dtDayName,
HolidayObservedDate = dtDate
FROM #DateTable
WHERE dtMonth = 'February'
AND dtDayName = 'Monday'
AND dtDayRank = 3
SELECT
HolidayName = 'Thanksgiving Day',
ObservedDayOfWeek = dtDayName,
HolidayObservedDate = dtDate
FROM #DateTable
WHERE dtMonth = 'November'
AND dtDayName = 'Thursday'
AND dtDayRank = 4
Output
I liked how this solution worked out because I can identify any date in the year by using a predicate equal to the month, day of the week and how many times this day of the week has occurred in this month. I made this into a stored procedure and table valued function so that I can run it by passing a year and it returns all holidays for that year.
Is this a good solution...is there an easier way?

Answer 3

There's some math you can use to make your SQL life easier e.g. 3rd Monday in February mathematically has to be between the 15th and the 21st (the earliest 3rd Monday has 14 days before it; the latest 3rd Monday can have no more than 20 days before it). If you have a tally table, it will be pretty easy to find all the dates. Here's how you can do it for president's day
with t1 as
(SELECT 1 num
FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1)) subTable(n)
),
TallyTable as
(
SELECT TOP 10000 ROW_NUMBER() OVER (ORDER BY (SELECT 1)) n
FROM t1 a
CROSS JOIN t1 b
CROSS JOIN t1 c
CROSS JOIN t1 d
CROSS JOIN t1 e
CROSS JOIN t1 f
),
DateTable as
(
SELECT DateAdd(day,n,'1/1/2018') DateValue
FROM TallyTable
)
SELECT *
FROM DateTable DT
WHERE DatePart(month,DT.DateValue) = 2 --February
AND DatePart(dw,DT.DateValue) = 2 --Monday
AND DatePart(day,DT.DateValue) BETWEEN 15 AND 21; --Day is between 15 and 21