Function duration/ produces "rational" number which breaks timestamps

[svetlyak40wt]

Here is how to reproduce this problem.

CL-USER> (local-time-duration:duration/
          (local-time-duration:duration :day 7)
          1676)
#<LOCAL-TIME-DURATION:DURATION [0/360/360000000000/419]  6 minutes 360000000000/419 nsecs>

CL-USER> (local-time-duration:timestamp-duration+
          (local-time:now)
          *)
#<LOCAL-TIME:TIMESTAMP <<error printing object>> {102F8D4613}>

CL-USER> (handler-bind ((error 'trivial-backtrace:print-backtrace))
           (local-time:format-rfc1123-timestring nil *))
Date/time: 2021-09-01-13:12!
An unhandled error condition has been signalled:
   The value
     45043985000/419
   is not of type
     (MOD 1000000000)
   from the function type declaration.


Backtrace for: #<SB-THREAD:THREAD "sly-channel-1-mrepl-remote-1" RUNNING {102FC904F3}>
0: (LOCAL-TIME:DECODE-TIMESTAMP @#<error printing a LOCAL-TIME:TIMESTAMP: #<TYPE-ERROR expected-type: (MOD 1000000000) datum: 45043985000/419>> :TIMEZONE #<LOCAL-TIME\
::TIMEZONE UTC> :OFFSET NIL)
1: (LOCAL-TIME::%CONSTRUCT-TIMESTRING @#<error printing a LOCAL-TIME:TIMESTAMP: #<TYPE-ERROR expected-type: (MOD 1000000000) datum: 45043985000/419>> (:SHORT-WEEKDAY \
", " (:DAY 2) #\  :SHORT-MONTH #\  (:YEAR 4) #\  (:HOUR 2) #\: (:MIN 2) #\: (:SEC 2) #\  :GMT-OFFSET-HHMM) #<unavailable argument>)
2: (LOCAL-TIME:FORMAT-TIMESTRING NIL @#<error printing a LOCAL-TIME:TIMESTAMP: #<TYPE-ERROR expected-type: (MOD 1000000000) datum: 45043985000/419>> :FORMAT (:SHORT-W\
EEKDAY ", " (:DAY 2) #\  :SHORT-MONTH #\  (:YEAR 4) #\  (:HOUR 2) #\: (:MIN 2) #\: (:SEC 2) #\  :GMT-OFFSET-HHMM) :TIMEZONE #<LOCAL-TIME::TIMEZONE UTC>)
3: ((LAMBDA ()))
4: (SB-INT:SIMPLE-EVAL-IN-LEXENV (HANDLER-BIND ((ERROR (QUOTE TRIVIAL-BACKTRACE:PRINT-BACKTRACE))) (LOCAL-TIME:FORMAT-RFC1123-TIMESTRING NIL *)) #<NULL-LEXENV>)
5: (EVAL (HANDLER-BIND ((ERROR (QUOTE TRIVIAL-BACKTRACE:PRINT-BACKTRACE))) (LOCAL-TIME:FORMAT-RFC1123-TIMESTRING NIL *)))
6: ((LAMBDA NIL :IN SLYNK-MREPL::MREPL-EVAL-1))