Put your two times in separate cells and subtract the cells to determine the difference between the two times. You can format the times and the answer to display in a variety of time formats.
It depends which spreadsheet package you're using, and how its syntax is set but - something like... D3=A3-B3 or D3=sum(A3-B3)
Yes.
auto calculate
Spreadsheets can calculate just about anything you want. That is their purpose. If you know what you want to calculate and how to do it, then you can use a spreadsheet to do it.
30 degree East and 80 degree west time difference
You can easily do this with Microsoft Excel or OpenOffice's spreadsheet module.
Probably nothing. Sounds like semantics to me.
In Microsoft Excel, there are two calculation methods. Usually it is set to Auto Calculate, which means that every time a cell is changed, it goes through and recalculates every formula in the spreadsheet. If you have a very large spreadsheet, this can slow things down, especially if you have several cells to make changes to. If you change the settings to Manual Calculation, then you can make all of your changes, then tell it to recalculate the spreadsheet.
A spreadsheet app has rows and columns. Word processing just goes down the page.
to organize data, draw graphs, calculate possible results
To calculate Delta t, you would subtract Universal Time or UT from Terrestrial Time or TT. Delta t would be the difference.
The real power behind a spreadsheet's ability to calculate is derived from formulas. Spreadsheet programs like Microsoft Excel are capable of handling hundreds of formula.