Count of distinct (unique) values by day

Hi all,

Thanks in advance for any assistance you can render. I've been wrestling with this issue for the last hour, and haven't made much headway.

I've got a spreadsheet in the following format:

Date / Name / Date / Unique Names
Jan1 / Sue / Jan1 / 2
Jan1 / Bob / Jan2 / 1
Jan1 / Sue / Jan3 / 3
Jan2 / George
Jan2 / George
Jan3 / Bob
Jan3 / George
Jan3 / George
Jan3 / Sue

I want to automatically perform the count for the number of unique names on a given day, as I'm dealing with roughly 6000 entries over the past year. In other words, I'd like to count how many unique (distinct) names appear on January 1, on January 2, on January 3, and so forth.

Again, many thanks in advance for any assistance y'all can offer!