# Excel 2013: three new functions

**DAYS()**

Date arithmetic is nothing new in Excel, but this function is new to Excel 2013. Previously one had to use a formula like “=B1-A1” where B1 would contain the later date, A1 the earlier date. Typing “=DAYS(“ in a cell, you are prompted with “end_date,start_date”), for the formula

=DAYS(B1;A1)

It’s not any quicker than the old way, but it is more memorable. On your system, you may need a comma in place of a semi-colon (it’s a Regional setting in Windows).

**ARABIC()**

We have long been able to use the ROMAN() function to create Roman numerals, but Microsoft has finally included its opposite:

**ISOWEEKNUM()**

Old (WEEKNUM) and New. Here are two formulas for week numbers, with results on the right:

ISOWEEKNUM() differs in what it sees to the first Monday of the year.