Time in spreadsheets.
WHY DATES CAUSE PROBLEMS
They are stored as numbers and displayed as text, and formats differ by region.
WHAT GOES WRONG
Dates imported as text and not recognised Day and month transposed Sorting producing the wrong order
HOW TO TELL
A genuine date aligns right by default and can be formatted.
Text aligns left and cannot.
WHAT TO DO ABOUT TEXT DATES
Convert them explicitly, rather than reformatting the display.
Reformatting text does not make it a date.
WHAT TO EXTRACT
Year, month and week, into separate columns.
WHY
So you can group by period without recalculating.
WHAT TO BE CAREFUL WITH
Comparing part-months against whole ones Comparing periods of different lengths Ignoring that some months have more working days
WHAT TO PREFER FOR COMPARISON
The same period last year, for seasonal businesses.
WHAT TO STANDARDISE
One date format, everywhere.
WHAT TO CHECK AFTER ANY IMPORT
That dates are dates, and in the right order.
