diff --git a/grid2demand/_grid2demand.py b/grid2demand/_grid2demand.py
index a1e97d5..29556b2 100644
--- a/grid2demand/_grid2demand.py
+++ b/grid2demand/_grid2demand.py
@@ -666,7 +666,7 @@ def run_gravity_model(self,
         print("  : Successfully generated OD demands.")
         return None
 
-    def gen_agent_based_demand(self) -> None:
+    def gen_agent_based_demand(self, time_periods: str = "0700-0800") -> None:
         """generate agent-based demand
 
         Args:
@@ -680,7 +680,9 @@ def gen_agent_based_demand(self) -> None:
             node_dict = self.node_dict
 
         self.df_agent = gen_agent_based_demand(node_dict, self.zone_dict,
-                                               df_demand=self.df_demand, verbose=self.verbose)
+                                               df_demand=self.df_demand,
+                                               time_periods=time_periods,
+                                               verbose=self.verbose)
         return None
 
     def save_results_to_csv(self, output_dir: str = "",
@@ -690,9 +692,9 @@ def save_results_to_csv(self, output_dir: str = "",
                             node: bool = True,  # save updated node
                             poi: bool = True,  # save updated poi
                             agent: bool = False,  # save agent-based demand
+                            agent_time_period: str = "0700-0800",
                             zone_od_dist_table: bool = False,
                             zone_od_dist_matrix: bool = False,
-                            is_demand_with_geometry: bool = False,
                             overwrite_file: bool = True) -> None:
         """save results to csv files
 
@@ -713,7 +715,7 @@ def save_results_to_csv(self, output_dir: str = "",
             self.output_dir = path2linux(output_dir)
 
         if demand:
-            save_demand(self, overwrite_file=overwrite_file, is_demand_with_geometry=is_demand_with_geometry)
+            save_demand(self, overwrite_file=overwrite_file)
 
         if zone:
             save_zone(self, overwrite_file=overwrite_file)
@@ -731,7 +733,10 @@ def save_results_to_csv(self, output_dir: str = "",
             save_zone_od_dist_matrix(self, overwrite_file=overwrite_file)
 
         if agent:
-            self.gen_agent_based_demand()
+            if agent_time_period:
+                self.gen_agent_based_demand(time_periods=agent_time_period)
+            else:
+                self.gen_agent_based_demand()
             save_agent(self, overwrite_file=overwrite_file)
 
         return None
diff --git a/grid2demand/func_lib/gen_agent_demand.py b/grid2demand/func_lib/gen_agent_demand.py
index 7dd269a..1dded30 100644
--- a/grid2demand/func_lib/gen_agent_demand.py
+++ b/grid2demand/func_lib/gen_agent_demand.py
@@ -9,6 +9,7 @@
 
 from random import choice, uniform
 import math
+import re
 
 import pandas as pd
 from pyufunc import gmns_geo
@@ -18,6 +19,7 @@ def gen_agent_based_demand(node_dict: dict, zone_dict: dict,
                            path_demand: str = "",
                            df_demand: pd.DataFrame = "",
                            agent_type: str = "v",
+                           time_period: str = "0000-2359",
                            verbose: bool = False) -> pd.DataFrame:
     """Generate agent-based demand data
 
@@ -32,7 +34,28 @@ def gen_agent_based_demand(node_dict: dict, zone_dict: dict,
     Returns:
         pd.DataFrame: _description_
     """
-    # either path_demand or df_demand must be provided
+    # Validate time_period format
+    time_period_pattern = re.compile(r"^\d{4}-\d{4}$")
+    if not isinstance(time_period, str) or not time_period_pattern.match(time_period):
+        raise ValueError(
+            f"Error: time_period '{time_period}' must be a string in the format 'HHMM-HHMM'.")
+
+    start_time_str, end_time_str = time_period.split('-')
+
+    # Validate that the times are within the valid range
+    try:
+        start_time = int(start_time_str[:2]) * 60 + int(start_time_str[2:])
+        end_time = int(end_time_str[:2]) * 60 + int(end_time_str[2:])
+    except ValueError as e:
+        raise ValueError("Error: time_period contains non-numeric values.") from e
+
+    if not (0 <= start_time <= 1440) or not (0 <= end_time <= 1440):
+        raise ValueError(
+            "Error: time_period must be between '0000' and '2400'.")
+
+    if start_time >= end_time:
+        raise ValueError(
+            "Error: start_time must be less than end_time in time_period.")
 
     # if path_demand is provided, read demand data from path_demand
     if path_demand:
@@ -53,8 +76,8 @@ def gen_agent_based_demand(node_dict: dict, zone_dict: dict,
         d_node_id = choice(zone_dict[d_zone_id]["node_id_list"] + [""])
 
         if o_node_id and d_node_id:
-            # Change the range to 0 to 1440
-            rand_time = math.ceil(uniform(0, 1440))
+            # Generate a random time within the specified time period
+            rand_time = math.ceil(uniform(start_time, end_time))
 
             # Calculate hours and minutes from rand_time
             hours = rand_time // 60
diff --git a/pyproject.toml b/pyproject.toml
index da7ba87..d099bbb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "grid2demand"
-version = "1.0.0a2"
+version = "1.0.0a3"
 description = "A tool for generating zone-to-zone travel demand based on grid cells or TAZs and gravity model"
 authors = [
     {name = "Xiangyong Luo", email = "luoxiangyong01@gmail.com"},
diff --git a/setup.py b/setup.py
index 0283bbe..29bc031 100644
--- a/setup.py
+++ b/setup.py
@@ -23,7 +23,7 @@
 
 setuptools.setup(
     name="grid2demand",  # Replace with your own username
-    version="1.0.0a2",
+    version="1.0.0a3",
     author="Xiangyong Luo, Dr.Xuesong (Simon) Zhou",
     author_email="luoxiangyong01@gmail.com, xzhou74@asu.edu",
     description="A tool for generating zone-to-zone travel demand based on grid cells or TAZs and gravity model",