What is abbreviation of day?

Answer 1

The standard abbreviation for "day" is "d", but it is rarely used except in certain contexts:

1. In conjunction with other time abbreviations, e.g. 1yr 5mo 3d 4hr 5s

1. For formatting dates, e.g. mm/dd/yy

1. In scientific experiments or papers where days is the expected unit, e.g. "Estimated time to reach destination: 5d"

In others contexts, such as on a gauge or meter, it is preferable to simply use "day" or "days" to avoid confusion.