In August 2027 the son-eomneun days fall on 1, 10, 11, 20, 21, 30, 31. 7 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.
August 15: 광복절; August 16: 대체공휴일(광복절). Taken from Korea Astronomy and Space Science Institute open data.
August 8: 입추; August 23: 처서. 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.