David and Lucy fall in love with each other. On one day, David went to his close friend’s birthday celebration. There he had an idea. He wanted to celebrate his girlfriend’s birthday. But he doesn’t know her birthdate. David sent an SMS asking her birthdate. She replied the following:


David does not understand the meaning of that reply. Suddenly he got another SMS containing the following:

Use my LUCKY number.

David knows her lucky number is 7. But he doesn’t know how to solve the first reply.

Can you help David to identify her girlfriend’s birthdate.

Date of Birth format: DD/MM/YYYY

  • $\begingroup$ Does this have anything to do with music? A-G notes? $\endgroup$ Commented Sep 26, 2016 at 12:52
  • $\begingroup$ No.. There some thing related with lucky number. $\endgroup$
    – KSR
    Commented Sep 26, 2016 at 12:52
  • $\begingroup$ If you convert the string into a number (a=1, b=2 etc) you end up with something that is too large to be a millis timestamp (or even nanos). $\endgroup$
    – Ivanhoe
    Commented Sep 26, 2016 at 13:01
  • $\begingroup$ If either the DD or MM is a single digit (ie. 05/08/2016) is the zero encoded into the answer or is it just encoded as 5/8/2016? If neither are single digits, feel free to answer this either way to avoid spoilers :) $\endgroup$
    – Joe
    Commented Sep 26, 2016 at 13:04
  • $\begingroup$ 0 must be included. $\endgroup$
    – KSR
    Commented Sep 26, 2016 at 13:12

1 Answer 1


I guess her birthday is the


My reasoning is that the letters correspond to lights on a calculator type display, the letters a b c d e f g going clockwise from the top with G in the middle. This is known as a 7 segment display (hence the lucky number stuff) https://upload.wikimedia.org/wikipedia/commons/thumb/0/02/7_segment_display_labeled.svg/220px-7_segment_display_labeled.svg.png
The message is :
abdeg = 2
bcfg = 4
abcdef = 0
abc = 7
bc = 1
abcdfg = 9
abc = 7
acdefg = 6

  • $\begingroup$ I kind of got lost at the part where G comes into play... Could you edit, maybe upload a picture? $\endgroup$
    – Matsmath
    Commented Sep 26, 2016 at 13:23
  • $\begingroup$ @Matsmath start in the top left corner. The topmost bar is A, top-right is B, etc. until top-left is F. The remaining middle bar is G $\endgroup$
    – Joe
    Commented Sep 26, 2016 at 13:24
  • 1
    $\begingroup$ Ok, So what about the lucky number stuff?? $\endgroup$
    – Sid
    Commented Sep 26, 2016 at 13:25
  • $\begingroup$ Similar riddle -puzzling.stackexchange.com/questions/15321/… $\endgroup$ Commented Sep 26, 2016 at 13:33
  • $\begingroup$ @Sid to indicate 7-segment display, maybe? I can't see any better explanation for it $\endgroup$
    – Joe
    Commented Sep 26, 2016 at 13:46

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