diff --git a/fincal/core.py b/fincal/core.py
index 6f8bbab..915eb6a 100644
--- a/fincal/core.py
+++ b/fincal/core.py
@@ -1,4 +1,5 @@
 import datetime
+from collections import UserList
 from dataclasses import dataclass
 from numbers import Number
 from typing import Iterable, List, Literal, Mapping, Sequence, Tuple, Union
@@ -6,8 +7,8 @@ from typing import Iterable, List, Literal, Mapping, Sequence, Tuple, Union
 
 @dataclass
 class FincalOptions:
-    date_format: str = '%Y-%m-%d'
-    closest: str = 'before'  # after
+    date_format: str = "%Y-%m-%d"
+    closest: str = "before"  # after
 
 
 @dataclass(frozen=True)
@@ -20,12 +21,12 @@ class Frequency:
 
 
 class AllFrequencies:
-    D = Frequency('daily', 'days', 1, 1, 'D')
-    W = Frequency('weekly', 'days', 7, 7, 'W')
-    M = Frequency('monthly', 'months', 1, 30, 'M')
-    Q = Frequency('quarterly', 'months', 3, 91, 'Q')
-    H = Frequency('half-yearly', 'months', 6, 182, 'H')
-    Y = Frequency('annual', 'years', 1, 365, 'Y')
+    D = Frequency("daily", "days", 1, 1, "D")
+    W = Frequency("weekly", "days", 7, 7, "W")
+    M = Frequency("monthly", "months", 1, 30, "M")
+    Q = Frequency("quarterly", "months", 3, 91, "Q")
+    H = Frequency("half-yearly", "months", 6, 182, "H")
+    Y = Frequency("annual", "years", 1, 365, "Y")
 
 
 def _preprocess_timeseries(
@@ -33,9 +34,9 @@ def _preprocess_timeseries(
         Sequence[Iterable[Union[str, datetime.datetime, float]]],
         Sequence[Mapping[str, Union[float, datetime.datetime]]],
         Sequence[Mapping[Union[str, datetime.datetime], float]],
-        Mapping[Union[str, datetime.datetime], float]
+        Mapping[Union[str, datetime.datetime], float],
     ],
-    date_format: str
+    date_format: str,
 ) -> List[Tuple[datetime.datetime, float]]:
     """Converts any type of list to the correct type"""
 
@@ -75,12 +76,12 @@ def _preprocess_timeseries(
 def _preprocess_match_options(as_on_match: str, prior_match: str, closest: str) -> datetime.timedelta:
     """Checks the arguments and returns appropriate timedelta objects"""
 
-    deltas = {'exact': 0, 'previous': -1, 'next': 1}
+    deltas = {"exact": 0, "previous": -1, "next": 1}
     if closest not in deltas.keys():
         raise ValueError(f"Invalid closest argument: {closest}")
 
-    as_on_match = closest if as_on_match == 'closest' else as_on_match
-    prior_match = closest if prior_match == 'closest' else prior_match
+    as_on_match = closest if as_on_match == "closest" else as_on_match
+    prior_match = closest if prior_match == "closest" else prior_match
 
     if as_on_match in deltas.keys():
         as_on_delta = datetime.timedelta(days=deltas[as_on_match])
@@ -95,6 +96,24 @@ def _preprocess_match_options(as_on_match: str, prior_match: str, closest: str)
     return as_on_delta, prior_delta
 
 
+def _parse_date(date: str, date_format: str = None):
+    """Parses date and handles errors"""
+
+    if isinstance(date, (datetime.datetime, datetime.date)):
+        return datetime.datetime.fromordinal(date.toordinal())
+
+    if date_format is None:
+        date_format = FincalOptions.date_format
+
+    try:
+        date = datetime.datetime.strptime(date, date_format)
+    except TypeError:
+        raise Exception("Date does not seem to be valid date-like string")
+    except ValueError:
+        raise Exception("Date could not be parsed. Have you set the correct date format in FincalOptions.date_format?")
+    return date
+
+
 class _IndexSlicer:
     def __init__(self, parent_obj):
         self.parent = parent_obj
@@ -112,7 +131,7 @@ class _IndexSlicer:
         return item
 
 
-class Series:
+class Series(UserList):
     def __init__(self, data):
         if not isinstance(data, Sequence):
             raise TypeError("Series only supports creation using Sequence types")
@@ -128,27 +147,26 @@ class Series:
                 data = [datetime.datetime.strptime(i, FincalOptions.date_format) for i in data]
                 self.dtype = datetime.datetime
             except ValueError:
-                raise TypeError("Series does not support string data type except dates.\n"
-                                "Hint: Try setting the date format using FincalOptions.date_format")
-        elif isinstance(data[0], datetime.datetime):
+                raise TypeError(
+                    "Series does not support string data type except dates.\n"
+                    "Hint: Try setting the date format using FincalOptions.date_format"
+                )
+        elif isinstance(data[0], (datetime.datetime, datetime.date)):
             self.dtype = datetime.datetime
-            self.data = data
+            self.data = [_parse_date(i) for i in data]
         else:
             raise TypeError(f"Cannot create series object from {type(data).__name__} of {type(data[0]).__name__}")
 
     def __repr__(self):
         return f"{self.__class__.__name__}({self.data})"
 
-    def __getitem__(self, n):
-        return self.data[n]
-
-    def __len__(self):
-        return len(self.data)
-
     def __gt__(self, other):
         if self.dtype == bool:
             raise TypeError("> not supported for boolean series")
 
+        if isinstance(other, (str, datetime.datetime, datetime.date)):
+            other = _parse_date(other)
+
         if self.dtype == float and isinstance(other, Number) or isinstance(other, self.dtype):
             gt = Series([i > other for i in self.data])
         else:
@@ -178,10 +196,7 @@ class TimeSeriesCore:
     """Defines the core building blocks of a TimeSeries object"""
 
     def __init__(
-        self,
-        data: List[Iterable],
-        frequency: Literal['D', 'W', 'M', 'Q', 'H', 'Y'],
-        date_format: str = "%Y-%m-%d"
+        self, data: List[Iterable], frequency: Literal["D", "W", "M", "Q", "H", "Y"], date_format: str = "%Y-%m-%d"
     ):
         """Instantiate a TimeSeries object
 
@@ -241,42 +256,42 @@ class TimeSeriesCore:
 
         printable = {}
         iter_f = iter(self.time_series)
-        first_n = [next(iter_f) for i in range(n//2)]
+        first_n = [next(iter_f) for i in range(n // 2)]
 
         iter_b = reversed(self.time_series)
-        last_n = [next(iter_b) for i in range(n//2)]
+        last_n = [next(iter_b) for i in range(n // 2)]
         last_n.sort()
 
-        printable['start'] = [str((i, self.time_series[i])) for i in first_n]
-        printable['end'] = [str((i, self.time_series[i])) for i in last_n]
+        printable["start"] = [str((i, self.time_series[i])) for i in first_n]
+        printable["end"] = [str((i, self.time_series[i])) for i in last_n]
         return printable
 
     def __repr__(self):
         if len(self.time_series) > 6:
             printable = self._get_printable_slice(6)
             printable_str = "{}([{}\n\t    ...\n\t    {}], frequency={})".format(
-                                self.__class__.__name__,
-                                ',\n\t    '.join(printable['start']),
-                                ',\n\t    '.join(printable['end']),
-                                repr(self.frequency.symbol)
-                                )
+                self.__class__.__name__,
+                ",\n\t    ".join(printable["start"]),
+                ",\n\t    ".join(printable["end"]),
+                repr(self.frequency.symbol),
+            )
         else:
             printable_str = "{}([{}], frequency={})".format(
-                                              self.__class__.__name__,
-                                              ',\n\t'.join([str(i) for i in self.time_series.items()]),
-                                              repr(self.frequency.symbol)
-                                             )
+                self.__class__.__name__,
+                ",\n\t".join([str(i) for i in self.time_series.items()]),
+                repr(self.frequency.symbol),
+            )
         return printable_str
 
     def __str__(self):
         if len(self.time_series) > 6:
             printable = self._get_printable_slice(6)
             printable_str = "[{}\n ...\n {}]".format(
-                                ',\n '.join(printable['start']),
-                                ',\n '.join(printable['end']),
-                                )
+                ",\n ".join(printable["start"]),
+                ",\n ".join(printable["end"]),
+            )
         else:
-            printable_str = "[{}]".format(',\n '.join([str(i) for i in self.time_series.items()]))
+            printable_str = "[{}]".format(",\n ".join([str(i) for i in self.time_series.items()]))
         return printable_str
 
     def __getitem__(self, key):
@@ -288,27 +303,25 @@ class TimeSeriesCore:
             else:
                 dates_to_return = [self.dates[i] for i, j in enumerate(key) if j]
                 data_to_return = [(key, self.time_series[key]) for key in dates_to_return]
-                return TimeSeriesCore(data_to_return)
+                return TimeSeriesCore(data_to_return, frequency=self.frequency.symbol)
 
         if isinstance(key, int):
             raise KeyError(f"{key}. For index based slicing, use .iloc[{key}]")
-        elif isinstance(key, datetime.datetime):
+        elif isinstance(key, (datetime.datetime, datetime.date)):
+            key = _parse_date(key)
             item = (key, self.time_series[key])
-        if isinstance(key, str):
-            if key == 'dates':
+        elif isinstance(key, str):
+            if key == "dates":
                 return self.dates
-            elif key == 'values':
+            elif key == "values":
                 return self.values
-            try:
-                dt_key = datetime.datetime.strptime(key, FincalOptions.date_format)
-                item = (dt_key, self.time_series[dt_key])
-            except ValueError:
-                raise KeyError(f"{repr(key)}. If you passed a date as a string, "
-                               "try setting the date format using Fincal.Options.date_format")
-            except KeyError:
-                raise KeyError(f"{repr(key)}. This date is not available.")
+
+            dt_key = _parse_date(key)
+            item = (dt_key, self.time_series[dt_key])
+
         elif isinstance(key, Sequence):
-            item = [(k, self.time_series[k]) for k in key]
+            keys = [_parse_date(i) for i in key]
+            item = [(k, self.time_series[k]) for k in keys]
         else:
             raise TypeError(f"Invalid type {repr(type(key).__name__)} for slicing.")
         return item