양력(태양력) literaly means "Solar calendar". It generally means "Gregorian calendar" nowadays. A solar calendar is a calendar whose dates indicate the season or almost equivalently the position of the apparent position of the sun in relative to the stars. The Gregorian calendar, widely accepted as standard in the world, is an example of solar calendar. The Gregorian calendar is internationally the most widely used civil calendar. It is named after Pope Gregory XIII, who introduced it in October 1582. https://en.wikipedia.org/wiki/Gregorian_calendar 음력(태음력/태음태양력) literaly "Lunar Calaner/Lunisolar calendar". A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year, then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year, then the calendar will predict the constellation near which the full moon may occur. As with all calendars which divide the year into months there is an additional requirement that the year have a whole number of months. In this case ordinary years consist of twelve months but every second or third year is an embolismic year, which adds a thirteenth intercalary, embolismic, or leap month. The Gregorian calendar was officially adopted in 1896, but traditional holidays and age-reckoning for older generations are still based on the old calendar. The biggest festival in Korea today is Seollal(설날), the first day of the traditional Korean New Year. Other important festivals include Daeboreum(대보름) also referred to as Boreumdaal(보름달) (the first full moon), Dano(단오) (spring festival) and Chuseok(추석) (harvest moon festival). https://en.wikipedia.org/wiki/Lunisolar_calendar https://en.wikipedia.org/wiki/Korean_calendar

양력 (also 태양력) is the normal, official solar calendar that everyone uses the world over including Korea. 음력 (also 태음력) is the lunar calendar which was official in Korea until 1895. Nowadays this calendar is only used in connection with traditional holidays such as the Lunar New Year (음력 설) and Chuseok (추석, Full Moon Festival - 음력 8월 15일). I believe there are very few people left now who remember dates by this calendar. We now use 양력 pretty much for everything. Some people used to keep track of birthdays in both calendars in the old days (until mid to late 20th century), but I doubt any ordinary people do these days. I'm prettry sure you won't have any trouble at all even if you don't know anything about 음력. It is a thing of the past which might appear in old movies and storybooks.