To get the nth day of year based on a given date, you can use a formula based on the DATE and YEAR functions. In the example shown, the formula in C5 is:
=B4-DATE(YEAR(B4),1,0)
With the date "June 1, 2016" in cell B4...

To add a given number of years to a date, you can use a formula based on the DATE function, with help from the YEAR, MONTH, and DAY functions.
In the example shown, the formula in D5 is:
=DATE(YEAR(B5)+C5,MONTH(B5),...

If you need to calculate the percent remaining in a year, based on a given date, you do so with a formula based on the YEARFRAC function.
In the example, the formula in C5, which calculates percentage of year remaining...

If you need to test two dates to see they both have the same month and year, you can do so with a simple formula that uses the MONTH and YEAR functions.
How the formula works
In the example, the formula in cell D6...

If need to generate a dynamic series of dates with a formula that increase by one year from a single start date, you can do so with a formula that uses the DAY, MONTH, YEAR, and DATE functions.
How the formula works...

To get a fiscal year from a date, you can use a formula based on the YEAR and MONTH functions. In the example shown, the formula in D5 is:
=YEAR(B5)+(MONTH(B5)>=C5)
How this formula works
By convention a fiscal...

To generate a dynamic series of dates with a formula that increases by one month from a single start date, you can use a formula based on DAY, MONTH, YEAR, and DATE functions.
How the formula works
In the example, B6...

If you need to extract the year from a date, you can use the YEAR function. In the generic form of the formula above, the date must be in a form that Excel recognizes as a valid date.
How the formula works
The YEAR...

If you want to test whether the year of a certain date is a leap year, you can use a formula that uses the MONTH, YEAR, and DATE functions.
In the example shown, the formula in cell C5 is:
=MONTH(DATE(YEAR(B5),2,29...

If you need to convert a date to a Julian date format in Excel, you can do so by building a formula that uses the TEXT, YEAR, and DATE functions.
Background
"Julian date format" refers to a format where the year value...

To count dates in a given year, you can use the SUMPRODUCT and YEAR functions. In the example shown, the formula in E5 is:
=SUMPRODUCT(--(YEAR(dates)=D5))
where "dates" the a named range B5:B15.
How this formula...

Note: Excel has several built-in data validation rules for dates. This page explains how to create a your own validation rule based on a custom formula if you need more control or flexibility.
To allow a user to enter...

Note: Excel has several built-in data validation rules for dates. This page explains how to create a your own validation rule based on a custom formula in case you want or need more control and flexibility.
To allow a...