Convert UTC timestamp to Simple binary encoded message - python-2.7

Question

I am trying to convert UTC timestamp to simple binary encoded message.
Would like to achieve what is mentioned in example here.
Binary Encoding Example
The following timestamp:
UTC timestamp 14:17:22 Friday, October 4, 2024
is expressed in binary code (nanoseconds since Unix epoch) this way:
007420bf8838fb17 (8 bytes in nanoseconds since Unix epoch synced to a master clock to microsecond accuracy.
What I have done so far is,
import struct
from datetime import datetime
dt = datetime(2024, 10, 4, 14, 17, 22, 0)
timestamp = (dt - datetime(1970, 1, 1)).total_seconds() * 1000000000
utc_timestamp = struct.pack('d', timestamp)
Output I see on CLI is '\xf4\x02\x82\xa1E\xfb\xb7C' but, as per example in shared link, expected is 007420bf8838fb17

Answer 1

TL;DR: I think there's either an error in linked example, or the description of the representation is incorrect or incomplete.
import struct
from datetime import datetime, timedelta, timezone
utc_tz = timezone(timedelta(0))
t = datetime(2024, 10, 4, 14, 17, 22, 0, utc_tz)
nanos = int(t.timestamp()) * 1_000_000_000
print(hex(timestamp))
This gives the result of 0x17fb45a18202f400, not the quoted 0x17fb3888bf297400 (as presented, I think it's a little-endian byte string, so this value has the order of bytes reversed).
The quoted answer, converted to decimal seconds (dividing by 1_000_000_000) is 1728037042.0005898. That value obviously has a sub-second quantity, which the source datetime does NOT have.
Decoding the seconds component of the quoted answer:
import time
answer = 0x17fb3888bf297400
secs = int(answer / 1_000_000_000)
print(time.gmtime(secs))
gives:
time.struct_time(tm_year=2024, tm_mon=10, tm_mday=4, tm_hour=10, tm_min=17, tm_sec=22, tm_wday=4, tm_yday=278, tm_isdst=0)
which looks almost correct, save that the hour component is 4 hours earlier. So ... my guess is that this is actually a US/Eastern timestamp (not UTC), and contains a sub-second component of 5898ns, and the example is misleading.
If the schema you're using is encoding timestamps as a 64-bit number of nanoseconds since the Unix epoch (midnight 1 January 1970), then I think your example code has only one error: use format <q (or <Q) rather than d, and you'll get a little-endian 64-bit integer as required. You will also need to convert the timestamp to an integer to have struct.pack() accept it.