diff --git a/my/calendar/holidays.py b/my/calendar/holidays.py
index e9560b2..48389d3 100644
--- a/my/calendar/holidays.py
+++ b/my/calendar/holidays.py
@@ -1,12 +1,51 @@
+from functools import lru_cache
+from datetime import date, datetime, timedelta
 import re
-from typing import Tuple, Iterator
-from datetime import date, datetime
+from typing import Tuple, Iterator, List, Union
 
 
 from my_configuration.holidays_data import HOLIDAYS_DATA
 
 
-def iter_data() -> Iterator[Tuple[date, int]]:
+from workalendar.europe import UnitedKingdom # type: ignore
+cal = UnitedKingdom() # TODO FIXME specify in config
+
+
+Dateish = Union[datetime, date, str]
+
+
+def as_date(dd: Dateish) -> date:
+    if isinstance(dd, datetime):
+        return dd.date()
+    elif isinstance(dd, date):
+        return dd
+    else:
+        return as_date(datetime.strptime(dd, '%Y%m%d'))
+
+
+@lru_cache(1)
+def get_days_off_work() -> List[date]:
+    return list(iter_days_off_work())
+
+
+def is_day_off_work(d: date) -> bool:
+    return d in get_days_off_work()
+
+
+def is_working_day(d: Dateish) -> bool:
+    day = as_date(d)
+    if not cal.is_working_day(day):
+        # public holiday -- def holiday
+        return False
+    # otherwise rely on work data
+    return not is_day_off_work(day)
+
+
+def is_holiday(d: Dateish) -> bool:
+    return not(is_working_day(d))
+
+
+def _iter_work_data() -> Iterator[Tuple[date, int]]:
     emitted = 0
     for x in HOLIDAYS_DATA.splitlines():
         m = re.search(r'(\d\d/\d\d/\d\d\d\d)(.*)-(\d+.\d+) days \d+.\d+ days', x)
@@ -22,9 +61,25 @@ def iter_data() -> Iterator[Tuple[date, int]]:
 
         yield d, int(dd)
         emitted += 1
-    assert emitted > 5
+    assert emitted > 5 # arbitrary, just a sanity check.. (TODO move to tests?)
+
+
+def iter_days_off_work() -> Iterator[date]:
+    for d, span in _iter_work_data():
+        dd = d
+        while span > 0:
+            # only count it if it wasnt' a public holiday/weekend already
+            if cal.is_working_day(dd):
+                yield dd
+                span -= 1
+            dd += timedelta(days=1)
+
+
+def test():
+    assert is_holiday('20190101')
+    assert not is_holiday('20180601')
 
 
 if __name__ == '__main__':
-    for d in iter_data():
-        print(d)
+    for d in iter_days_off_work():
+        print(d, ' | ', d.strftime('%d %b'))