diff --git a/src/utils/date_utils.py b/src/utils/date_utils.py
index 30d7ed4..500e4c6 100644
--- a/src/utils/date_utils.py
+++ b/src/utils/date_utils.py
@@ -1,65 +1,32 @@
 from datetime import datetime, timedelta
-from typing import Tuple
+from typing import Optional, Tuple
 
 
-def get_date_range(days: int) -> Tuple[datetime, datetime]:
-    """Get date range for the last N days."""
-    end_date = datetime.now()
-    start_date = end_date - timedelta(days=days)
-    return start_date, end_date
+def parse_date(date_str: Optional[str]) -> Optional[datetime]:
+    """Parse a date string into a datetime object."""
+    if not date_str:
+        return None
 
-
-def parse_timestamp(timestamp_str: str) -> datetime:
-    """Parse a timestamp string to datetime."""
     formats = [
+        "%Y-%m-%d",
         "%Y-%m-%d %H:%M:%S",
         "%Y-%m-%dT%H:%M:%S",
-        "%Y-%m-%d %H:%M:%S%z",
-        "%Y-%m-%dT%H:%M:%SZ",
+        "%Y/%m/%d",
+        "%m/%d/%Y",
+        "%d/%m/%Y",
     ]
 
     for fmt in formats:
         try:
-            return datetime.strptime(timestamp_str, fmt)
+            return datetime.strptime(date_str, fmt)
         except ValueError:
             continue
 
-    raise ValueError(f"Cannot parse timestamp: {timestamp_str}")
+    return None
 
 
-def format_duration(seconds: float) -> str:
-    """Format duration in human-readable format."""
-    if seconds < 60:
-        return f"{seconds:.1f}s"
-    elif seconds < 3600:
-        minutes = seconds / 60
-        return f"{minutes:.1f}m"
-    elif seconds < 86400:
-        hours = seconds / 3600
-        return f"{hours:.1f}h"
-    else:
-        days = seconds / 86400
-        return f"{days:.1f}d"
-
-
-def group_by_period(
-    commits: list,
-    period: str = "day",
-) -> dict:
-    """Group commits by time period."""
-    result = {}
-    for commit in commits:
-        if period == "hour":
-            key = commit.timestamp.strftime("%Y-%m-%d %H:00")
-        elif period == "day":
-            key = commit.timestamp.strftime("%Y-%m-%d")
-        elif period == "week":
-            key = commit.timestamp.strftime("%Y-%W")
-        elif period == "month":
-            key = commit.timestamp.strftime("%Y-%m")
-        else:
-            key = commit.timestamp.strftime("%Y-%m-%d")
-
-        result[key] = result.get(key, 0) + 1
-
-    return result
+def get_date_range(days: int) -> Tuple[datetime, datetime]:
+    """Get a date range for the last N days."""
+    end_date = datetime.now()
+    start_date = end_date - timedelta(days=days)
+    return start_date, end_date