TL;DR: every other day. Read on for details.
Many scientists use Google Scholar to find papers, get alerts about new work, and —if they have a profile— display a publication list which tracks citations. What is the Google Scholar update frequency?
It occurred to me that we have a perfect way to check this in the form of the profile of Prof. et al., by some measures the most prolific and influential scientist in history. I made that profile a while back to illustrate some points about the uses and abuses of Google Scholar profiles, and since then it has steadily accumulated citations (2.7 million at the time of writing).
With 333 highly cited publications, Google Scholar will find new citations for et al. any time it updates its index, and so the update frequency of this profile is a good proxy for the update frequency of Google Scholar itself. By setting a web service to take an automatic screenshot of et al.‘s profile every day, I’ve sampled two weeks worth of data. It turns out the update frequency is very regular: I found that et al.‘s citations increase (by about ~1500) exactly every other day.
So that’s the answer to how often Google Scholar updates its citation counts: every other day. The updates I’ve seen happen on days with odd day numbers. In case you’re wondering what time the update happens, stop worrying and go back to writing, you procrastinator!