Update transition dates and add a module for generating them

Author: JamieTaylor-TUOS

requirements_dev.txt

@@ -0,0 +1 @@
+pandas

sp2ts/__init__.py

@@ -1,8 +1,3 @@
-try:
-    #py2
-    from sp2ts import sp2ts, to_unixtime, from_unixtime, sp2dt, ts2sp, dt2sp
-except:
-    #py3+
-    from sp2ts.sp2ts import sp2ts, to_unixtime, from_unixtime, sp2dt, ts2sp, dt2sp
+from sp2ts.sp2ts import sp2ts, to_unixtime, from_unixtime, sp2dt, ts2sp, dt2sp
 
 __all__ = ["sp2ts", "to_unixtime", "from_unixtime", "sp2dt", "ts2sp", "dt2sp"]

sp2ts/get_transition_dates.py

@@ -0,0 +1,38 @@
+"""
+Utility for generating a list of transition date timestamps for use in sp2ts.
+Always test the outputs carefully in case there have been changes in the behvaiour of pytz or
+datetime!
+
+Jamie Taylor
+2024-02-20
+"""
+
+from datetime import datetime, time
+from pytz import timezone
+
+import pandas as pd
+
+from sp2ts import to_unixtime
+
+def main():
+    tz = timezone("Europe/London")
+    transition_dates = pd.DataFrame([
+        [d.year, d.date(), to_unixtime(datetime.combine(d.date(), time(0)), timezone_="UTC")]
+        for d in tz._utc_transition_times[20:]
+    ], columns=["year", "transition_date", "transition_date_ts"])
+    transition_dates = transition_dates.loc[(transition_dates.year >= 1990)]
+    transition_dates["transition_number"] = transition_dates.groupby("year")["transition_date"]\
+                                                            .rank().astype("Int64")
+    transition_dates_ = transition_dates.set_index(["year", "transition_number"])\
+                                        .unstack(level=-1)\
+                                        .reset_index()\
+                                        .reset_index()\
+                                        .values
+    print(
+        "TRANSITION_DATES_TS = [\r\n   ",
+        "\r\n    ".join([f"({t[4]}, {t[5]}), # {t[1]}: {t[2]}, {t[3]}" for t in transition_dates_]),
+        "\r\n]"
+    )
+
+if __name__ == "__main__":
+    main()

sp2ts/sp2ts.py

@@ -14,39 +14,56 @@
 import pytz
 import numpy as np
 
+# See get_transition_dates.py
 TRANSITION_DATES_TS = [
-    (922579200, 941328000),     # 1999
-    (954028800, 972777600),     # 2000
-    (985478400, 1004227200),    # 2001
-    (1017532800, 1035676800),   # 2002
-    (1048982400, 1067126400),   # 2003
-    (1080432000, 1099180800),   # 2004
-    (1111881600, 1130630400),   # 2005
-    (1143331200, 1162080000),   # 2006
-    (1174780800, 1193529600),   # 2007
-    (1206835200, 1224979200),   # 2008
-    (1238284800, 1256428800),   # 2009
-    (1269734400, 1288483200),   # 2010
-    (1301184000, 1319932800),   # 2011
-    (1332633600, 1351382400),   # 2012
-    (1364688000, 1382832000),   # 2013
-    (1396137600, 1414281600),   # 2014
-    (1427587200, 1445731200),   # 2015
-    (1459036800, 1477785600),   # 2016
-    (1490486400, 1509235200),   # 2017
-    (1521936000, 1540684800),   # 2018
-    (1553990400, 1572134400),   # 2019
-    (1585440000, 1603584000),   # 2020
-    (1616889600, 1635638400),   # 2021
-    (1648339200, 1667088000),   # 2022
-    (1679788800, 1698537600),   # 2023
-    (1711843200, 1729987200),   # 2024
-    (1743292800, 1761436800),   # 2025
-    (1774742400, 1792886400),   # 2026
-    (1806192000, 1824940800),   # 2027
-    (1837641600, 1856390400),   # 2028
-    (1869091200, 1887840000),   # 2029
-    (1901145600, 1919289600)    # 2030
+    (638323200, 657072000), # 1990: 1990-03-25, 1990-10-28
+    (670377600, 688521600), # 1991: 1991-03-31, 1991-10-27
+    (701827200, 719971200), # 1992: 1992-03-29, 1992-10-25
+    (733276800, 751420800), # 1993: 1993-03-28, 1993-10-24
+    (764726400, 782870400), # 1994: 1994-03-27, 1994-10-23
+    (796176000, 814320000), # 1995: 1995-03-26, 1995-10-22
+    (828230400, 846374400), # 1996: 1996-03-31, 1996-10-27
+    (859680000, 877824000), # 1997: 1997-03-30, 1997-10-26
+    (891129600, 909273600), # 1998: 1998-03-29, 1998-10-25
+    (922579200, 941328000), # 1999: 1999-03-28, 1999-10-31
+    (954028800, 972777600), # 2000: 2000-03-26, 2000-10-29
+    (985478400, 1004227200), # 2001: 2001-03-25, 2001-10-28
+    (1017532800, 1035676800), # 2002: 2002-03-31, 2002-10-27
+    (1048982400, 1067126400), # 2003: 2003-03-30, 2003-10-26
+    (1080432000, 1099180800), # 2004: 2004-03-28, 2004-10-31
+    (1111881600, 1130630400), # 2005: 2005-03-27, 2005-10-30
+    (1143331200, 1162080000), # 2006: 2006-03-26, 2006-10-29
+    (1174780800, 1193529600), # 2007: 2007-03-25, 2007-10-28
+    (1206835200, 1224979200), # 2008: 2008-03-30, 2008-10-26
+    (1238284800, 1256428800), # 2009: 2009-03-29, 2009-10-25
+    (1269734400, 1288483200), # 2010: 2010-03-28, 2010-10-31
+    (1301184000, 1319932800), # 2011: 2011-03-27, 2011-10-30
+    (1332633600, 1351382400), # 2012: 2012-03-25, 2012-10-28
+    (1364688000, 1382832000), # 2013: 2013-03-31, 2013-10-27
+    (1396137600, 1414281600), # 2014: 2014-03-30, 2014-10-26
+    (1427587200, 1445731200), # 2015: 2015-03-29, 2015-10-25
+    (1459036800, 1477785600), # 2016: 2016-03-27, 2016-10-30
+    (1490486400, 1509235200), # 2017: 2017-03-26, 2017-10-29
+    (1521936000, 1540684800), # 2018: 2018-03-25, 2018-10-28
+    (1553990400, 1572134400), # 2019: 2019-03-31, 2019-10-27
+    (1585440000, 1603584000), # 2020: 2020-03-29, 2020-10-25
+    (1616889600, 1635638400), # 2021: 2021-03-28, 2021-10-31
+    (1648339200, 1667088000), # 2022: 2022-03-27, 2022-10-30
+    (1679788800, 1698537600), # 2023: 2023-03-26, 2023-10-29
+    (1711843200, 1729987200), # 2024: 2024-03-31, 2024-10-27
+    (1743292800, 1761436800), # 2025: 2025-03-30, 2025-10-26
+    (1774742400, 1792886400), # 2026: 2026-03-29, 2026-10-25
+    (1806192000, 1824940800), # 2027: 2027-03-28, 2027-10-31
+    (1837641600, 1856390400), # 2028: 2028-03-26, 2028-10-29
+    (1869091200, 1887840000), # 2029: 2029-03-25, 2029-10-28
+    (1901145600, 1919289600), # 2030: 2030-03-31, 2030-10-27
+    (1932595200, 1950739200), # 2031: 2031-03-30, 2031-10-26
+    (1964044800, 1982793600), # 2032: 2032-03-28, 2032-10-31
+    (1995494400, 2014243200), # 2033: 2033-03-27, 2033-10-30
+    (2026944000, 2045692800), # 2034: 2034-03-26, 2034-10-29
+    (2058393600, 2077142400), # 2035: 2035-03-25, 2035-10-28
+    (2090448000, 2108592000), # 2036: 2036-03-30, 2036-10-26
+    (2121897600, 2140041600), # 2037: 2037-03-29, 2037-10-25
 ]
 
 def to_unixtime(datetime_: datetime, timezone_: Optional[str] = None) -> int: