This script shows you how far a msb truncated unix timestamp gets you.

how_many_bits_does_my_unix_time_stamp_really_need?.py

import datetime

def unix_to_date(timestamp):
    """Converts a Unix timestamp to a timezone-aware, human-readable date."""
    return datetime.datetime.fromtimestamp(timestamp, datetime.UTC).strftime('%Y-%m-%d %H:%M:%S')

# Initialize a Unix timestamp with all bits unset (value 0)
current_value = 0

# Get the current time as a Unix timestamp
current_timestamp = datetime.datetime.now(datetime.UTC).timestamp()
highest_bit = int(current_timestamp).bit_length() - 1
current_timestamp = 1<<highest_bit
print(f"Offset: {unix_to_date(current_timestamp)} unix: {current_timestamp} highest bit: {int(current_timestamp).bit_length() - 1}")

# Iterate over all 64 bits (LSB to MSB)
for i in range(64):
    # Set the i-th bit
    current_value |= (1 << i)
    
    # Count of bits set so far: i+1
    set_bit_count = i + 1
    
    # Convert the timestamp to a readable date, if within valid range
    try:
        end_date = unix_to_date(current_value)
        end_date_offset = unix_to_date(current_value + current_timestamp)
    except (OverflowError, ValueError):
        end_date = "Out of range"
        end_date_offset = "Out of range"

    # Print the set bit count and the corresponding date
    print(f"{set_bit_count} Unix normal: {end_date} Unix offset: {end_date_offset}")