Enter RPN: R47: Setting the Date & Time

Data Types

The R47 is not just a number manipulator, as in old HP designs, which might be able to interpret a value like 17.0416 as the current local time. The R47 goes much further by supporting data types, which in this context means that it needs more than just a specialized decimal format before it will consider an undifferentiated numeric value to be a time value.

Yet, it does understand how to convert from decimal values in this classic format to a proper R47 time value:

17.0416
ENTER
🟦 CLK
🟦 H.MS→𝕋
17:04:16

The result in x is not a mere cosmetic change, textually replacing one decimal point with a colon and inserting a second. The value is now data typed as a time value, a fact we can verify via the key sequence INFO ↓ F1. That calls the TYPE? function, which reports 3 with “Time” off to the left. If you dig into the R47 reference material, you can find a table of data types, where 3 is more formally described as a “Time or time interval.”

This is the meaning of that mathematical double-struck “𝕋” in the menus.

If I add 1 to the time value left in x above:

1
+
18:04:16

It has interpreted that bare integer 1 as “one hour” and handled the addition accordingly.

One may then guess that to add one second, one would add 0.0001 per the old HP rules, right? Nope, sorry, because the input continues to be interpreted as hours; this entry means “one ten-thousandth of an hour,” or 0.36 seconds. We must convert it from classic HP notation first, same as above, but there is a shortcut we can take, if we wish:

18:04:16
.0001
🟦 .ms
0:00:01
+
18:04:17

Evidently the R47 designers considered this conversion valuable enough to give it a hard-labeled keyboard function slot, above the 1/𝑥 key. Adding this type-converted value yields the expected new time value.

There is another way to enter the time value, which may be more natural for you, at a cost to stack space tolerably borne in SSIZE8 mode, but painful in SSIZE4 mode:

17 ENTER
04 ENTER
16
🟦 zyx→𝕋
17:04:16

That is, put the HH, MM, and SS parts onto the stack, in that order, and then tell the calculator to consume all three and return a proper time value.

Setting the Time

This at last allows us to set the calculator’s on-board RTC. Press the down arrow in the lower left corner of the keyboard until you pull up the CLK menu screen that shows the SETTIM function. It’s an 🟧-shifted F2 in the firmware I have here, but this may be subject to change.

The calculator does not show the current time in the upper line of the display, doubtless to save battery life, but you can retrieve it and observe that it has advanced with:

🟦 Time→𝕋

That says, “Take the RTC’s current time value and display it as a 𝕋ime value in x.”

Setting the Date

Dates work the same way, except that they’re indicated in menus with the mathematical double-struck 𝔻 symbol:

2025
11
08
🟦 zyx→𝔻
2025-11-08
🟧 SETDAT

This time you do see the top line of the calculator change, because the current date is shown by default.

I have my calculator in the default locale mode, which affects the display of dates, both in the calculator’s top line and on the stack. Setting it to USA mode gives the idiotic MM/DD/YY format. Go ahead, gawk at it for a sec.

Now put it back to DFLT at least, please.

Thank you. 🤓

And Now the Easy Way

The above documents the method I puzzled out within an hour of unboxing the calculator. Paul Dale shortly pointed out on the HP Museum Forum that you can pull up a setup menu via 🟧 PREF DMCP which gives access to the 5. Settings > menu, where you can set the date and time in a more natural manner. This also gives access to other related settings like setting the time and date formats.

(You may now wish to return to my R47 article index.)

R47: Setting the Date & Time

Data Types

Setting the Time

Setting the Date

And Now the Easy Way

License