' date conversion routines
' TassyJim Nov2014
currentdate$= DATE$
currenttime$=TIME$
DO
PRINT currentdate$;" ";currenttime$
IF MM.DEVICE$<>"Micromite MkII" THEN
PRINT "This program will not run on the ";MM.DEVICE$
ENDIF

JD% = Julian(currentdate$)
weekday= (jd%+1) MOD 7 'weekday starts at 0 for Sunday
dayz$=MID$("SunMonTueWedThuFriSatSun",weekday*3+1,3)
Utime%=unixtime%(currentdate$+" "+currenttime$ )
DoY= DayofYear(currentdate$)
Jdate$=JulianDate$(currentdate$+" "+currenttime$ )
PRINT "Day of Week: ";weekday;" ";dayz$
PRINT "Day of year: ";DoY
PRINT "Julian Day : ";JD%
PRINT "Julian Date: ";Jdate$

PRINT "Unix time : ";Utime%
PRINT
PRINT "Reverse J Day : "; JDString$(JD%)
PRINT "Reverse J Date : "; JDateString$(Jdate$)
PRINT "Reverse U time : "; unixDateString$(Utime%)
PRINT

INPUT "New Date (DD/MM/YYYY) or X to quit: ",newdate$
IF UCASE$(newdate$)="X" THEN EXIT DO
IF newdate$<>"" THEN currentdate$=newdate$
INPUT "New Time (HH:MM:SS) : ",newtime$
IF newtime$<>"" THEN
currenttime$=newtime$
ELSE
currenttime$=TIME$
ENDIF
LOOP
END

FUNCTION Julian(datestring$)
' datestring in the format "dd/mm/yyyy" or "dd-mm-yyyy"
' returns the Julian day number corresponding to midday on the given date
' using the Gregorian calendar
LOCAL d, m, y, ff, yo, mo
d=VAL(MID$(datestring$,1,2))
m=VAL(MID$(datestring$,4,2))
y=VAL(MID$(datestring$,7,4))
ff=(14-m)\12
yo=y+4800-ff
mo=m+12*ff-3
Julian = d +(153*mo+2)\5 + 365*yo + yo\4 - yo\100 + yo\400 - 32045
'Julian = d +(153*mo+2)\5 + 365*yo + yo\4 - 32083 ' Julian calendar
END FUNCTION

FUNCTION JulianDate$(datestring$)
' datestring in the format "dd/mm/yyyy hh:mm:ss" or "dd-mm-yyyy hh:mm:ss"
' returns the Julian Date as a string
' requires Julian()
LOCAL h, m, s, JD%, JDtime
JD%=Julian(LEFT$(datestring$,10))
h=VAL(MID$(datestring$,12,2))
m=VAL(MID$(datestring$,15,2))
s=VAL(MID$(datestring$,18,2))
JDtime=(h*3600+m*60+s)/86400
IF JDtime >= 0.5 THEN ' adjust times before midday to the previous day
JDtime = JDtime - 0.5
ELSE
JDtime = JDtime + 0.5
JD% = JD% -1
ENDIF
IF JDtime=0 THEN
JulianDate$=STR$(JD%)+".0"
ELSE
JulianDate$=STR$(JD%)+MID$(mystr$(JDtime),2)
ENDIF
END FUNCTION

FUNCTION DayofYear(datestring$)
' given the date dd/mm/yyyy, returns the day number of the year
' requires Julian()
LOCAL day1, y
day1=Julian(datestring$)
y=VAL(MID$(datestring$,7,4))-1
DayofYear= day1-Julian("31/12/"+STR$(y,4))
END FUNCTION

FUNCTION unixtime%(datestring$)
' datestring in the format "dd/mm/yyyy hh:mm:ss" or "dd-mm-yyyy hh:mm:ss"
' returns the unixtime
' requires Julian()
LOCAL h%, m%, s%, JD%
JD%=Julian(LEFT$(datestring$,10))
unixtime%=(JD%-2440588)*86400
h%=VAL(MID$(datestring$,12,2))
m%=VAL(MID$(datestring$,15,2))
s%=VAL(MID$(datestring$,18,2))
unixtime%=unixtime%+h%*3600+m%*60+s%
END FUNCTION

FUNCTION unixDateString$(unixt%)
LOCAL unixd%, unixf%, h, m, s, ut$
unixd%=unixt%\86400
unixf%=unixt% MOD 86400
IF unixd%<0 AND unixf%<>0 THEN
unixf%=86400+unixf%
ENDIF
h= unixf%\3600
m= (unixf% MOD 3600)\60
s=(unixf% MOD 3600) MOD 60
ut$=STR$(h,2,0,"0")+":"+STR$(m,2,0,"0")+":"+STR$(s,2,0,"0")
unixDateString$=JDString$(JD%)+" "+ut$
END FUNCTION

FUNCTION JDString$(JD%)
' Given the Julian day number, returns the date as a string
' valid for Gregorian dates after Oct 15, 1582
LOCAL l, n, i, j, d, m, y
l = jd%+68569
n = FIX((4*l)/146097)
l = l-FIX((146097*n+3)/4)
i = FIX((4000*(l+1))/1461001)
l = l-FIX((1461*i)/4)+31
j = FIX((80*l)/2447)
d = l-FIX((2447*j)/80)
l = FIX(j/11)
m = j+2-(12*l)
y = 100*(n-49)+i+l
JDString$=STR$(d,2,0,"0")+"/"+STR$(m,2,0,"0")+"/"+STR$(y,4)
END FUNCTION

FUNCTION JDateString$(JDate$)
' Given the Julian date as a string, returns the date and time as a string
LOCAL dp, JD%
dp=INSTR(JDate$,".")
IF dp >0 THEN
JD%=VAL(LEFT$(JDate$,dp-1))
JDsecs=VAL(MID$(JDate$,dp))*86400
ELSE
JD%=VAL(JDate$)
JDsecs=0
ENDIF
IF JDsecs >= 43200 THEN ' adjust times before midday to the previous day
JDsecs= JDsecs - 43200
JD% = JD% +1
ELSE
JDsecs= JDsecs + 43200
ENDIF
h= JDsecs\3600
m= (JDsecs MOD 3600)\60
s=(JDsecs MOD 3600) MOD 60
JDateString$=JDString$(JD%)+" "+STR$(h,2,0,"0")+":"+STR$(m,2,0,"0")+":"+STR$(s,2,0,"0")
END FUNCTION

FUNCTION mystr$(k)
' needed to print small numbers with 7 digits after decimal point
SELECT CASE k
CASE IS > 0.0001, IS < -0.0001 ' big enough for the normal STR$ function
mystr$=STR$((k),0,7)
CASE IS > 0.0000001
mystr$=STR$((k*1000),0,4)
mystr$="0.000"+MID$(mystr$,3)
CASE IS < -0.0000001
mystr$=STR$((ABS(k)*1000),0,4)
mystr$="-0.000"+MID$(mystr$,3)
CASE ELSE ' really small numbers display as zero
mystr$="0.0000000"
END SELECT
END FUNCTION