The 19th rule in Dr Wozniak's 20 Rules for Formulating
Knowledge is a quick bit
of advice: “provide date stamping”.
This is a small tip that goes hand-in-hand with keeping notes. It's easy but worthwhile.
You should think of your Chinese flashcards deck as an ever-developing resource
for your Chinese learning. It's not static, and neither is it a fire-and-forget
system. It needs updating and maintaining as much as it needs studying.
Keeping date stamps with your flashcards is useful for this long-term process.
They can be actual dates, or references to periods of study. For example, you
might mark years and terms in a course, textbook chapters or levels you are
studying at the time you add the flashcard.
Having this information makes it easy to isolate those cards later. You might
want to cram for an exam based on the content of a particular term or chapter.
It can also be nice to reassure yourself that you still remember certain things
from the early days of your Chinese studies. Having time-related information on
your cards lets you do those things easily.
Note that you certainly don't need to memorise this timing information. It's
only there for archival purposes. You may or may not want to make it visible on
the response side of the card, but it's not a good idea to display it with the
prompt as it could become a crutch for that information.