If it's a public holiday, it's Sunday schedule.
See
http://www.gov.hk/en/about/abouthk/holiday/ for offical holidays
{L_CODE}:
Day following the first day of January 2 January Monday
Lunar New Year's Day 23 January Monday
The second day of the Lunar New Year 24 January Tuesday
The third day of the Lunar New Year 25 January Wednesday
Ching Ming Festival 4 April Wednesday
Good Friday 6 April Friday
The day following Good Friday 7 April Saturday
Easter Monday 9 April Monday
The Birthday of the Buddha 28 April Saturday
Labour Day 1 May Tuesday
Tuen Ng Festival 23 June Saturday
Day following Establishment Day 2 July Monday
Day following Mid-Autumn Festival 1 October Monday
Day following National Day 2 October Tuesday
Chung Yeung Festival 23 October Tuesday
Christmas Day 25 December Tuesday
The first weekday after Christmas Day 26 December Wednesday