What is the meaning of Dd?

Abbreviation of day (in two-digit numeric format, as in: dd/mm/yyyy)

A letter of the practical Hadza alphabet, found in interjections only.

Abbreviation of du da? (and you? what about you?).

Abbreviation of dag (day), in a two-digit numeric format used for dates

Initialism of du då? (and you? what about you?).

Initialism of du ? (and you? what about you?).

The sixth letter of the Welsh alphabet, called èdd and written in the Latin script. It is preceded by d and followed by e.

Source: wiktionary.org