In May 2027 the son-eomneun days fall on 5, 14, 15, 24, 25. 5 in all. These are days whose lunar date ends in 9 or 0 — long the first thing people check before moving house or opening a shop.
May 1: 노동절; May 3: 대체공휴일(노동절); May 5: 어린이날; May 13: 부처님오신날. Taken from Korea Astronomy and Space Science Institute open data.
May 6: 입하; May 21: 소만. Computed from the sun's ecliptic longitude, not looked up in a table.
These dates hold for every visitor. A son-eomneun day is fixed by the lunar calendar alone and has nothing to do with your birth chart. What a given day means for you needs a birth date — there is no auspicious day that holds for everybody.