How perform arithmetic (add,subtract) between two Date&Time timestamps? - windows

Question

I am trying to create an arbitrary time using batch files. I am trying to subtract set values (such as 1 day, 1 month, and 2000 years) from my code to display the system time subtracted by the set values stated previously. For the hours and minutes, I am subtracting 10 hours and 10 minutes (shown in code as different values). I am also aware that date and time are variables related to my system. ~ Please ignore
Important -
My problem now is with this part:
if %minb% EQU 60 set /a minb=%minb%-60 & set /a hourb=%hourb%+1
if %hourb% EQU 24 set /a hourb=%hourb%-24 & set /a dayb=%dayb%+1
if %dayb% EQU 30 set /a dayb=%dayb%-30 & set /a monthb=%monthb%+1
if %monthb% EQU 12 set /a monthb=%monthb%-12 & set /a yearb=%yearb%+1
I can't seem to be able to make the minutes reset to 0 and have the hours add 1 when the minute value hits 60, and same with the hour-day, day-month, month-year relationships, other than that, the problems with my code are mostly fixed. When I run the code and wait for the minutes (or add to the time difference) to reach 60, they just pass 60 and don't reset nor add to the hoursb value.
.
My date and time formats are:
Short date: M/d/yyyy
Long date: dddd, MMMM d, yyyy
Short time: h:mm
Long time: h:mm:ss
I am using Windows 10.
Please note that the values in the set /a do not match my description, but of course they can be changed around. They are set to the shown numbers for test purposes only.
EDIT:
Code:
#echo off
:start
set day=%date:~-7,2%
set month=%date:~-10,2%
set year=%date:~-4,4%
set hour=%time:~0,2%
set min=%time:~3,2%
set /a "hourb=%hour%-10"
set /a "minb=%min%+30"
set /a "dayb=%day%-1"
set /a "monthb=%month%-1"
set /a "yearb=%year%-2000"
if %minb% lss 10 set minb=0%minb%
if %hourb% lss 10 set hourb=0%hourb%
if %dayb% lss 10 set dayb=0%dayb%
if %monthb% lss 10 set monthb=0%monthb%
if %minb% EQU 60 set /a minb=%minb%-60 & set /a hourb=%hourb%+1
if %hourb% EQU 24 set /a hourb=%hourb%-24 & set /a dayb=%dayb%+1
if %dayb% EQU 30 set /a dayb=%dayb%-30 & set /a monthb=%monthb%+1
if %monthb% EQU 12 set /a monthb=%monthb%-12 & set /a yearb=%yearb%+1
cls
:: ———————————————————————–
#mode con cols=20 lines=6
title Arbitrary Clock
:time
echo.
echo. %hourb%:%minb%
echo.
echo. %dayb%-%monthb%-%yearb%
echo.
ping -n 2 0.0.0.0 >nul
cls
goto :start
Alright, so as you can see in the new edit to the code, I set the values to the stated at the beginning of this question. Subtracting 10 from the hours, subtracting 1 from the days and months, and subtracting 2000 from the years. I added 30 to the minutes to show the problem right now.
So my system time is 4:40, 1/5/2019. Alright?
The displayed time on the clock is 06:70, 04-00-19.
The desired outcome is 07:10, 04-12-18.
This was edited heavily. Thanks in advance.

Answer 1

You have a fundamental error in your description. When you subtract a number of days/months/years from a date, you are subtracting a date, not a number! For example, if today date is 05/01/2019 (obviously in DD/MM/YYYY format) and you want to subtract 1 month, the result should be 05/12/2018 because you are subtracting a date (1 month). If you subtract a number 1 from the month part, then the result will be 05/00/2019. For this reason, this problem should be solved via the well-known methods to add and subtract dates.
The problem with these methods is that they are valid just for a certain range of dates, and that ranges usually start in 1583. If you want to subtract 2000 from year 2018 and get 18, then such "year 18" is not a valid year in the usual date management methods. For this reason, besides to use the usual methods to manage dates, you also need to complete a couple small adjustments.
I taken the code segments linked in my comment and modified they slightly in order to solve this problem. I completed some tests and it seems to work correctly, but perhaps the method may fail in certain specific range of values.
#echo off
setlocal EnableDelayedExpansion
rem Subtract a number of Days/Months/Years # Hours:Minutes:Seconds from a datetime stamp
rem Antonio Perez Ayala aka Aacini
rem Define the "Date in DDMMYYYY format" To "Julian Day Number" conversion "function"
set "DateToJDN(Date)=( a=1Date, y=a%%10000, a/=10000, m=a%%100, d=a/100-100, a=(m-14)/12, (1461*(y+4800+a))/4+(367*(m-2-12*a))/12-(3*((y+4900+a)/100))/4+d-32075 )"
set /P "stamp1=Enter base timestamp as DD/MM/YYYY HH:MM:SS "
set /P "stamp2=Enter timestamp to subtract in same format: "
set "adjust=0"
for /F "tokens=1-4" %%a in ("%stamp1% %stamp2%") do set "date1=%%a" & set "time1=%%b" & set "date2=%%c" & set "time2=%%d"
if 1%date2:~-4% lss 11600 (
set /A "adjust=1%date2:~-4%+1600"
set "date2=%date2:~0,-4%!adjust:~1!"
set "adjust=1600"
)
set /A "days=!DateToJDN(Date):Date=%date1:/=%! - !DateToJDN(Date):Date=%date2:/=%!, days1600=%DateToJDN(Date):Date=00001600%"
set /A "ss=(((1%time1::=-100)*60+1%-100) - (((1%time2::=-100)*60+1%-100)"
if %ss% lss 0 set /A "ss+=60*60*24, days-=1"
set /A "hh=ss/3600+100, ss%%=3600, mm=ss/60+100, ss=ss%%60+100"
if %days% lss %days1600% set /A days+=days1600, days1600=0
set /A "l=days+68569,n=(4*l)/146097,l=l-(146097*n+3)/4,i=(4000*(l+1))/1461001,l=l-(1461*i)/4+31,j=(80*l)/2447,D=l-(2447*j)/80+100,l=j/11,M=j+2-(12*l)+100,Y=100*(n-49)+i+l+10000+adjust"
if %days1600% equ 0 set /A Y-=1600
echo -----------------------
echo Result: %D:~1%/%M:~1%/%Y:~1% %hh:~1%:%mm:~1%:%ss:~1%
A small example:
Enter base timestamp as DD/MM/YYYY HH:MM:SS 05/01/2019 10:53:45
Enter timestamp to subtract in same format: 01/01/2000 10:10:00
-----------------------
Result: 04/12/0018 00:43:45
PS - I really would like to see a PowerShell solution for this problem. It seems that it would take just a simple and short line of code...

Answer 2

A simpler windows batch option is to call a PowerShell command from within your batch script to manipulate past and future dates.
Below, lines 8 and 9 create and format your arbitrary date.
:: Set the below 3 variables to generate an Arbitrary Clock
:: Use a negative number to subtract (-7), positive number to add (7)
set Altered_Days=-7
set Altered_Months=-10
set Altered_Years=-4
:: The script will merge days and years to determine the arbitrary date and print the Arbitrary date to the screen
set /a Altered_Days=(%Altered_Years%*356)+%Altered_Days%
powershell -command "(((Get-date).AddDays(%Altered_Days%)).AddMonths(%Altered_Months%)).ToString('HH:mm, MM-dd-yyyy')"
:: If you want to capture the value in a variable, use the below line
powershell -command "(((Get-date).AddDays(%Altered_Days%)).AddMonths(%Altered_Months%)).ToString('HH:mm, MM-dd-yyyy')">captureVar && set /p Arbitrary_Clock=<captureVar
echo Arbitrary Clock Prediction && echo %Arbitrary_Clock%
This will enable your batch script to create the end result you are looking for on your Windows 10 OS.
One of the great things about PowerShell is that it can easily be called from the cmd line and a batch script. To do so, enter
powershell -command "the powershell command(s)"
If the PowerShell command calls for quotes, you must use a single quote to avoid ending the PowerShell session. To escape characters, follow batch scripting rules. Batch variables can be read in the PowerShell command, but values created in PowerShell must be redirected for later use in your batch script. This can be done as in line 12 above, or by using PowerShell's Set-Content command to write to a file. I frequently use PowerShell in my batch scripts to manipulate file data.
powershell -command "(Get-Content 'file.txt') -replace 'string','' | Select-String -Pattern 'keep lines with string' -SimpleMatch) -replace 'another string','to somthing different' | Set-Content 'file.txt'"
In the case of adding or subtracting time, PowerShell makes the task easy. And it doesn't require you to create a different script. You can write everything else as batch, use PowerShell commands you find helpful, and save the windows' script as batch.
For detailed explanations on how Get-Date and addDays work, reference:
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/get-date?view=powershell-6
and
https://devblogs.microsoft.com/scripting/adding-and-subtracting-dates-with-powershell/