In October 2027 the son-eomneun days fall on 8, 9, 18, 19, 28. 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.
October 3: 개천절; October 4: 대체공휴일(개천절); October 9: 한글날; October 11: 대체공휴일(한글날). Taken from Korea Astronomy and Space Science Institute open data.
October 8: 한로; October 24: 상강. 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.