Fix custom periods

tests/test_ticker.py

@@ -8,6 +8,8 @@
    python -m unittest tests.ticker.TestTicker
 
 """
+from datetime import datetime, timedelta
+
 import pandas as pd
 
 from tests.context import yfinance as yf
@@ -133,8 +135,55 @@ def test_invalid_period(self):
         with self.assertRaises(YFInvalidPeriodError):
             dat.history(period="2wks", interval="1d", raise_errors=True)
         with self.assertRaises(YFInvalidPeriodError):
-            dat.history(period="2mo", interval="1d", raise_errors=True)
+            dat.history(period="2mos", interval="1d", raise_errors=True)
+
+    def test_valid_custom_periods(self):
+        valid_periods = [
+            # Yahoo provided periods
+            ("1d", "1m"), ("5d", "15m"), ("1mo", "1d"), ("3mo", "1wk"),
+            ("6mo", "1d"), ("1y", "1mo"), ("5y", "1wk"), ("max", "1mo"),
+
+            # Custom periods
+            ("2d", "30m"), ("10mo", "1d"), ("1y", "1d"), ("3y", "1d"),
+            ("2wk", "15m"), ("6mo", "5d"), ("10y", "1wk")
+        ]
+
+        tkr = "AAPL"
+        dat = yf.Ticker(tkr, session=self.session)
 
+        for period, interval in valid_periods:
+            with self.subTest(period=period, interval=interval):
+                df = dat.history(period=period, interval=interval, raise_errors=True)
+                self.assertIsInstance(df, pd.DataFrame)
+                self.assertFalse(df.empty, f"No data returned for period={period}, interval={interval}")
+                self.assertIn("Close", df.columns, f"'Close' column missing for period={period}, interval={interval}")
+
+                # Validate date range
+                now = datetime.now()
+                if period != "max":  # Difficult to assert for "max", therefore we skip
+                    if period.endswith("d"):
+                        days = int(period[:-1])
+                        expected_start = now - timedelta(days=days)
+                    elif period.endswith("mo"):
+                        months = int(period[:-2])
+                        expected_start = now - timedelta(days=30 * months)
+                    elif period.endswith("y"):
+                        years = int(period[:-1])
+                        expected_start = now - timedelta(days=365 * years)
+                    elif period.endswith("wk"):
+                        weeks = int(period[:-2])
+                        expected_start = now - timedelta(weeks=weeks)
+                    else:
+                        continue
+
+                    actual_start = df.index[0].to_pydatetime().replace(tzinfo=None)
+                    expected_start = expected_start.replace(hour=0, minute=0, second=0, microsecond=0)
+
+                    # leeway added because of weekends
+                    self.assertGreaterEqual(actual_start, expected_start - timedelta(days=7),
+                                            f"Start date {actual_start} out of range for period={period}")
+                    self.assertLessEqual(df.index[-1].to_pydatetime().replace(tzinfo=None), now,
+                                         f"End date {df.index[-1]} out of range for period={period}")
 
     def test_prices_missing(self):
         # this test will need to be updated every time someone wants to run a test

yfinance/exceptions.py

@@ -44,7 +44,8 @@ def __init__(self, ticker, invalid_period, valid_ranges):
         self.ticker = ticker
         self.invalid_period = invalid_period
         self.valid_ranges = valid_ranges
-        super().__init__(f"{self.ticker}: Period '{invalid_period}' is invalid, must be one of {valid_ranges}")
+        super().__init__(f"{self.ticker}: Period '{invalid_period}' is invalid, "
+                         f"must be of the format {valid_ranges}, etc.")
 
 
 class YFRateLimitError(YFException):

yfinance/scrapers/history.py

@@ -105,11 +105,6 @@ def history(self, period="1mo", interval="1d",
                 period_user = period
                 period = None
             interval = '1d'
-        else:
-            end = utils._parse_user_dt(end, self.tz)
-            start = _datetime.date.fromordinal(end)
-            start -= utils._interval_to_timedelta(period)
-            start -= _datetime.timedelta(days=4)
 
         start_user = start
         end_user = end
@@ -237,10 +232,9 @@ def history(self, period="1mo", interval="1d",
         elif "chart" not in data or data["chart"]["result"] is None or not data["chart"]["result"] or not data["chart"]["result"][0]["indicators"]["quote"][0]:
             _exception = YFPricesMissingError(self.ticker, _price_data_debug)
             fail = True
-        elif period is not None and period not in self._history_metadata["validRanges"]:
-            # even if timestamp is in the data, the data doesn't encompass the period requested
-            # User provided a bad period. The minimum should be '1d', but sometimes Yahoo accepts '1h'.
-            _exception = YFInvalidPeriodError(self.ticker, period, self._history_metadata['validRanges'])
+        elif period and period not in self._history_metadata['validRanges'] and not utils.is_valid_period_format(period):
+            # User provided a bad period
+            _exception = YFInvalidPeriodError(self.ticker, period, ", ".join(self._history_metadata['validRanges']))
             fail = True
 
         if fail:
@@ -255,6 +249,13 @@ def history(self, period="1mo", interval="1d",
                 self._reconstruct_start_interval = None
             return utils.empty_df()
 
+        # Process custom periods
+        if period and period not in self._history_metadata.get("validRanges", []):
+            end = int(_time.time())
+            start = _datetime.date.fromtimestamp(end)
+            start -= utils._interval_to_timedelta(period)
+            start -= _datetime.timedelta(days=4)
+
         # parse quotes
         quotes = utils.parse_quotes(data["chart"]["result"][0])
         # Yahoo bug fix - it often appends latest price even if after end date