SELECT ... WHERE dt >= '2017-02-01'
             AND dt  < '2017-02-01' + INTERVAL 1 MONTH

Sure, this could be done with BETWEEN and inclusion of 23:59:59. But, the pattern has this benefits:

• You don’t have pre-calculate the end date (which is often an exact length from the start)
• You don’t include both endpoints (as BETWEEN does), nor type ‘23:59:59’ to avoid it.
• It works for DATE, TIMESTAMP, DATETIME, and even the microsecond-included DATETIME(6).
• It takes care of leap days, end of year, etc.
• It is index-friendly (so is BETWEEN).