12:21 on July 21, 2019

The numerology energy represented by numbers do not depend on date.

The energy is the same on any date.

Interpretation of the energy may be different depending on events or situations. Thus, interpretation of 12:21 in relation to a date requires information about what happened or what was the situation that made the date notable.

The energy representing the number 12:21 resonates with (among other things) home, nurturing, and independence.

The energies representing the number 12 and the the number 21 resonate with creative self-expression, optimism, and other aspects of life.

The energy representing the July 21, 2019 date resonates with (again, among other things) methodology and working toward a secure future.

Perhaps those individual number interpretations, including interpretations available by following the links, and considering what happened on July 21, 2019 that wasn't included with your question, have enough information for you to do your own interpretation of the energy represented by the numbers.