Added Daylight Savings Time offset calculation

main.py

@@ -84,6 +84,47 @@ def calculate_x_spacing(text, scale=1):
     return (128 - (scaled_text * 8)) // 2
 
 
+def is_dst(year, month, day, hour_utc, weekday):
+    """
+    Returns True if UTC time falls within US/Canada Daylight Saving Time:
+    - Starts: 2nd Sunday in March at 02:00 local (07:00 UTC for UTC-5)
+    - Ends:   1st Sunday in November at 02:00 local (06:00 UTC for UTC-4)
+    Note: weekday is 0=Monday ... 6=Sunday.
+    """
+    # 1. Months completely inside or outside DST
+    if month < 3 or month > 11:
+        return False
+    if 3 < month < 11:
+        return True
+
+    # 2. March (Starts 2nd Sunday)
+    # The 2nd Sunday always falls between March 8 and March 14
+    if month == 3:
+        # Find the day of the 2nd Sunday
+        second_sunday = 14 - ((weekday - day + 14) % 7)
+        if day < second_sunday:
+            return False
+        elif day > second_sunday:
+            return True
+        else:
+            # On the transition day itself, 02:00 EST is 07:00 UTC
+            return hour_utc >= 7
+
+    # 3. November (Ends 1st Sunday)
+    # The 1st Sunday always falls between Nov 1 and Nov 7
+    if month == 11:
+        first_sunday = 7 - ((weekday - day + 7) % 7)
+        if day < first_sunday:
+            return True
+        elif day > first_sunday:
+            return False
+        else:
+            # On the transition day itself, 02:00 EDT (01:00 EST) is 06:00 UTC
+            return hour_utc < 6
+
+    return False
+
+
 # --- Main Loop ---
 DAYS = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
 TIME_Y = 12  # Keep vertical placement consistent
@@ -91,14 +132,25 @@ TIME_Y = 12  # Keep vertical placement consistent
 last_second = -1
 
 while True:
-    # 1. Compute time
-    local_epoch = time.time() + (Config.UTC_OFFSET * 3600)
+    # 1. Fast, single-integer read from RTC
+    current_sec = time.time()
+
+    # 2. Gate everything behind the 1-second boundary
+    if current_sec != last_second:
+        last_second = current_sec
+
+        # Unpack UTC once per second
+        utc_year, utc_month, utc_day, utc_hour, _, _, utc_weekday, _ = time.gmtime(current_sec)
+
+        # Run DST check
+        dst_offset = 1 if is_dst(utc_year, utc_month, utc_day, utc_hour, utc_weekday) else 0
+        total_offset = Config.UTC_OFFSET + dst_offset
+
+        # Compute local wall-clock components
+        local_epoch = current_sec + (total_offset * 3600)
         year, month, day, hour_24, minute, second, weekday, _ = time.localtime(local_epoch)
 
-    # 2. Only redraw if the second has actually changed
-    if second != last_second:
-        last_second = second
-
+        # --- String formatting and OLED rendering ---
         sep = ":" if second % 2 == 0 else " "
 
         if Config.USE_24_HOUR:
@@ -121,5 +173,5 @@ while True:
 
         oled.show()
 
-    # 3. Sleep in small increments to catch the exact second boundary with minimal latency
-    time.sleep_ms(20)
+    # Fast poll to catch the next second boundary immediately
+    time.sleep_ms(25)