Andrew-Chen-Wang · April 13, 2025 18:47 · Apr 13, 2025
diff --git a/uuid8_excluding_day_precision.py b/uuid8_excluding_day_precision.py
@@ -0,0 +1,62 @@
+import uuid
+import random
+from datetime import datetime, UTC
+
+def encode_time_fields(dt: datetime) -> int:
+    year = dt.year
+    month = dt.month
+    hour = dt.hour
+    minute = dt.minute
+    millisecond = dt.microsecond // 1000
+
+    # Bounds check
+    if not (1970 <= year <= 4095):
+        raise ValueError("Year out of range")
+
+    # Encode into 40 bits
+    encoded = (
+        ((year - 1970) << 28) |
+        (month << 24) |
+        (hour << 19) |
+        (minute << 13) |
+        (millisecond)
+    )
+    return encoded  # 40 bits
+
+def generate_uuidv8_custom_time(dt: datetime = None) -> uuid.UUID:
+    if dt is None:
+        dt = datetime.now(UTC)
+
+    timestamp_bits = encode_time_fields(dt)
+
+    # Fill the remaining 88 bits with randomness
+    rand_high = random.getrandbits(88)
+
+    # Combine timestamp and random into a 128-bit integer
+    full_bits = (timestamp_bits << 88) | rand_high
+
+    # Insert UUIDv8 version and variant bits
+    full_bits &= ~(0xF << 76)
+    full_bits |= (0x8 << 76)  # version 8
+
+    full_bits &= ~(0xC000 << 48)
+    full_bits |= (0x8000 << 48)  # variant 1 (10xxxxxx...)
+
+    # Convert to UUID object
+    bytes_ = full_bits.to_bytes(16, byteorder="big")
+    return uuid.UUID(bytes=bytes_)
+
+def decode_time_from_uuidv8(u: uuid.UUID):
+    int_val = int.from_bytes(u.bytes, byteorder="big")
+    timestamp_bits = int_val >> 88
+
+    year = ((timestamp_bits >> 28) & 0xFFF) + 1970
+    month = (timestamp_bits >> 24) & 0xF
+    hour = (timestamp_bits >> 19) & 0x1F
+    minute = (timestamp_bits >> 13) & 0x3F
+    millisecond = timestamp_bits & 0x1FFF
+
+    return f"{year:04}-{month:02} {hour:02}:{minute:02}.{millisecond:03}"
+
+uuid = generate_uuidv8_custom_time()  # '03749580-0664-8ad3-ac86-c2532981ef85'
+decode_time_from_uuidv8(uuid)  # '2025-04 18:44.6'