diff --git a/fincal/fincal.py b/fincal/fincal.py
index ae263d9..c060383 100644
--- a/fincal/fincal.py
+++ b/fincal/fincal.py
@@ -1,6 +1,6 @@
 import datetime
 from dataclasses import dataclass
-from typing import List
+from typing import Dict, Iterable, List, Literal, Tuple, Union
 
 from dateutil.relativedelta import relativedelta
 
@@ -46,10 +46,59 @@ def create_date_series(
     return dates
 
 
+def _preprocess_timeseries(
+    data: Union[
+        List[Iterable[Union[str, datetime.datetime, float]]],
+        List[Dict[str, Union[float, datetime.datetime]]],
+        List[Dict[Union[str, datetime.datetime], float]],
+        Dict[Union[str, datetime.datetime], float]
+    ],
+    date_format: str
+) -> List[Tuple[datetime.datetime, float]]:
+    """Converts any type of list to the correct type"""
+
+    if isinstance(data, list):
+        if isinstance(data[0], dict):
+            if len(data[0].keys()) == 2:
+                current_data = [tuple(i.values()) for i in data]
+            elif len(data[0].keys()) == 1:
+                current_data = [tuple(*i.items()) for i in data]
+            else:
+                raise TypeError("Could not parse the data")
+            current_data = _preprocess_timeseries(current_data, date_format)
+
+        elif isinstance(data[0], Iterable):
+            if isinstance(data[0][0], str):
+                current_data = []
+                for i in data:
+                    row = datetime.datetime.strptime(i[0], date_format), i[1]
+                    current_data.append(row)
+            elif isinstance(data[0][0], datetime.datetime):
+                current_data = [(i, j) for i, j in data]
+            else:
+                raise TypeError("Could not parse the data")
+        else:
+            raise TypeError("Could not parse the data")
+
+    elif isinstance(data, dict):
+        current_data = [(k, v) for k, v in data.items()]
+        current_data = _preprocess_timeseries(current_data, date_format)
+
+    else:
+        raise TypeError("Could not parse the data")
+    current_data.sort()
+    return current_data
+
+
 class TimeSeries:
     """Container for TimeSeries objects"""
 
-    def __init__(self, data: List[tuple], date_format: str = "%Y-%m-%d", frequency="D"):
+    def __init__(
+        self,
+        data: List[Iterable],
+        date_format: str = "%Y-%m-%d",
+        frequency=Literal['D', 'W', 'M', 'Q', 'H', 'Y']
+    ):
         """Instantiate a TimeSeries object
 
         Parameters
@@ -69,11 +118,11 @@ class TimeSeries:
             Valid values are {D, W, M, Q, H, Y}
         """
 
-        time_series = [(datetime.datetime.strptime(i[0], date_format), i[1]) for i in data]
-        time_series.sort()
-        self.time_series = dict(time_series)
+        data = _preprocess_timeseries(data, date_format=date_format)
+
+        self.time_series = dict(data)
         self.dates = set(list(self.time_series))
-        if len(self.dates) != len(time_series):
+        if len(self.dates) != len(data):
             print("Warning: The input data contains duplicate dates which have been ignored.")
         self.start_date = list(self.time_series)[0]
         self.end_date = list(self.time_series)[-1]
@@ -123,7 +172,7 @@ class TimeSeries:
                 cur_val = self.time_series[cur_date]
             except KeyError:
                 pass
-            new_ts.update({cur_date: cur_val})  # type: ignore
+            new_ts.update({cur_date: cur_val})
 
         if inplace:
             self.time_series = new_ts
@@ -141,7 +190,7 @@ class TimeSeries:
                 cur_val = self.time_series[cur_date]
             except KeyError:
                 pass
-            new_ts.update({cur_date: cur_val})  # type: ignore
+            new_ts.update({cur_date: cur_val})
 
         if inplace:
             self.time_series = new_ts
@@ -151,7 +200,7 @@ class TimeSeries:
 
     def calculate_returns(
         self, as_on: datetime.datetime, closest: str = "previous", compounding: bool = True, years: int = 1
-    ) -> int:
+    ) -> float:
         """Method to calculate returns for a certain time-period as on a particular date
         >>> calculate_returns(datetime.date(2020, 1, 1), years=1)
         """
@@ -167,7 +216,7 @@ class TimeSeries:
         elif closest == "next":
             delta = 1
         else:
-            raise ValueError(f"Invalid value for closes parameter: {closest}")
+            raise ValueError(f"Invalid value for closest parameter: {closest}")
 
         while True:
             try: