Partitioning by month causing an error?

I have a partition per each month, like this:

CREATE TABLE mmd_yr2019_3 PARTITION OF mmd FOR VALUES FROM ('2019-03-01') TO ('2019-03-31');
CREATE TABLE mmd_yr2019_4 PARTITION OF mmd FOR VALUES FROM ('2019-04-01') TO ('2019-04-30');

This breaks for dates at the end of the month. What's the better way to write the bounds? 3/1 to 4/1 and then 4/1 to 5/1? Does that cause some overlap issue?

Thanks.

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