datetime device

src/uxn_tutorial_day_7.gmo

@@ -185,10 +185,42 @@ i invite you to compare these subroutines with the ones present in the 100r prog
 
 => https://git.sr.ht/~rabbits/nasu/tree/main/item/src/main.tal nasu source code
 
-* the audio device
-* practice: small music instrument
-* datetime device: reading the date and time
-* practice: visualization of time
+# the datetime device
+
+the datetime device can be useful for low resolution timing and/or for visualizations of time.
+
+it has several fields that we can read, all of them based on the current system time and timezone:
+
+```
+|b0 @DateTime [ &year $2 &month $1 &day $1 &hour $1 &minute $1 &second $1 &dotw $1 &doty $2 &isdst $1 ]
+```
+
+* the year short corresponds to the number of year in the so called common era
+* the month byte counts the months since january (i.e. january is 0, february 1, and so on)
+* the day byte counts the days starting from 1
+* the hour, minute and second bytes correspond to what one would expect
+* dotw (day of the week) is a byte counts the days since sunday (i.e sunday is 0, monday is 1, and so on)
+* doty (day of the year) is a byte counts the days since january 1 (i.e. jan 1st is 0, jan 2nd is 1, and so on)
+* isdst (is daylight saving time) is a flag, 01 if it's daylight saving time and 00 if it's not.
+
+it should be straightforward to use them! e.g. in order to read the hour of the day into the stack:
+
+```
+.DateTime/hour DEI
+```
+
+i invite you to develop a creative visualization of time!
+
+maybe you can use these values as coordinates for some sprites, or maybe you can use them as sizes or limits for shapes created with loops.
+
+or what about conditionally drawing sprites, and/or changing the system colors depending on the time? :)
+
+remember that for timing with a little bit more resolution, you can count the times that the screen vector has been fired!
+
+# the audio device
+
+at last, the audio device!
+
 
 # support