Date-Time Arithmetic

Question

I'm a long time Excel user.  I want to import a few of my Excel spreadsheets into Numbers so I can then take advantage of iCloud Drive to add data to these particular Numbers spreadsheet from my iPad Air 2 (latest version of IOS 8).  Any modifications to the Numbers spreadsheet will be done on my 2 year old 27" iMac running the latest version of Yosemite and Numbers.
All my Excel spreadsheets have imported to Numbers without a hitch except the one that uses Date-Time arithmetic.  Excel allows you to put a date in one cell and time in another and to add the two to create a number based on January 1, 1904 as the reference.  This makes it easy to do Date-Time Arithmetic.  As best I can tell you can only do this in Numbers if you enter a date and a time in each cell, which is both cumbersome and time consuming.  I can't seem to find any way around this.  Is there a way to add a date cell to a time cell in Numbers similar to Excel that I haven't found?  Thanks.

Answer 1

Klavezzo,
Date-Time values are where Numbers diverges most from Excel in the things that I use frequently. I no longer use Excel, so the differences don't affect me the way they might affect you or others. In Numbers, every Date has a Time associated with it, and every Time has a Date associated with it. They always exist together.
There are functions to strip out individual elements of the Date-Time value, if you need to: YEAR, MONTH, DAY, HOUR, MINUTE and TIMEVALUE. The first 5 are self explanatory, TIMEVALUE returns the decimal fraction of a day corresponding to the Time portion of the Date-Time value.
A Duration value can be useful if you prefer not to work in decimal fractions of a day, and it is especially important for Date-Time difference calculations.
The key things to remember about Date-Time calculations are 1. You can't add two Date-Time values, and 2. The result of a Date-Time subtraction is a Duration, and 3. To add to a Date-Time value, you can either add a Duration or you can add a numeric value of days, and decimal fractions of a day, for the time portion.
As with most values in Numbers, you can change how a value is displayed with formatting, but you can't change the data type with formatting. The only exception that I can think of is that when a value is formatted as Text. Then it no longer can be manipulated as a value, so it truly is altered internally.
If you give us some examples of your calculations, we can suggest ways to deal with them in Numbers.
Jerry