# TDatime inverse conversion

Hello,
I have another question, now on TDatetime (in timeonaxis2.C). I understand that T0 is converted to an int X0 by X0 = T0.Convert(). Is there an inverse method which converts back T0 from X0? In my application, I store successive points in time in an ntuple, and I store the successive X0’s instead of T0’s since to store integers is easy and I don’t need the Convert() method in reading many times the ntuple only when I write it (only once). However, after reading the X0’s I’d like to print the Date and Time values and I don’t see methods for this on X0 only on T0. How to solve this problem? Thanks,
Elemer

PS I think that this problem must have a solution since the X0 values after having read them from the ntuple are correctly plotted in the time axis by TGraph. Thanks for pointing me how it is done.
Elemer

Hello, I have digged a little and see that UInt_t x0 = T0.TDatime::Get(); can be converted back with TDatime::GetDateTime(x0,date,time); but I still don’t see how int X0 = T0.Convert(); can be converted back. When applying TDatime::GetDateTime(X0,date,time); date and time will be filled with wrong values, unfortunately. As far as I see from examples, it is X0 and not x0 which should be used e.g. on plotting in TGraph.
Elemer

Elemer also sent this code demonstrating the issue:

``````int GetMyDate(UInt_t Xm) {
{
UInt_t year  = Xm>>26;
UInt_t month = (Xm<<6)>>28;
UInt_t day   = (Xm<<10)>>27;
return 10000*(year+1995) + 100*month + day;
}
}
int GetMyTime(UInt_t Xm) {
UInt_t hour  = (Xm<<15)>>27;
UInt_t min   = (Xm<<20)>>26;
UInt_t sec   = (Xm<<26)>>26;
return 10000*hour + 100*min + sec;
}
void TempFormat() {
int date, time;
TDatime T0(2020, 7, 24, 16, 4, 10);
UInt_t X0 = T0.Convert();
printf("  \n Converted DateTime: %2d  \n ", X0 );
printf("  \n Year: %2d Month: %2d Day: %2d Hour: %2d Minute: %2d Second: %2d \n ",
T0.GetYear(), T0.GetMonth(), T0.GetDay(), T0.GetHour(), T0.GetMinute(), T0.GetSecond() );
TDatime::GetDateTime(X0,date,time);
printf(" \n From Convert date: %2d time: %2d \n ", date, time );
UInt_t x0 = T0.TDatime::Get();
TDatime::GetDateTime(x0,date,time);
printf(" \n From Get date: %2d time: %2d \n ", date, time );
date = GetMyDate(X0);
time = GetMyTime(X0);
printf(" \n From Convert and shifted date: %2d time: %2d \n ", date, time );
}
``````

The result obtained by: root -l TempFormat.C

``````root [0]
Processing TempFormat.C...

Converted DateTime: 1595599450

Year: 2020 Month:  7 Day: 24 Hour: 16 Minute:  4 Second: 10

From Convert date: 20181213 time: 144126

From Get date: 20200724 time: 160410

From Convert and shifted date: 20181213 time: 144126
root [1]
``````

Sorry to have missed that. It was in a new topic in a solved one.

When you do:

``````  TDatime T0(2020, 7, 24, 16, 4, 10);
UInt_t X0 = T0.Convert();
``````

`X0` contains the encoded date and time. To go back to the initial date you should use `GetYear()` `GetMonth()`, etc … all the getters are available. That would be the way to proceed… does it answer your question ?

No, it doesn’t answer my question. GetYear() etc. has to be applied on T0 and I would like to get back date and time from X0 and not from T0 by reasons I have mentioned in my post. As you can see from my code example, methods on X0 gives back wrong date and time.

Just create a new TDatime from X0;

``````root [0]   TDatime T0(2020, 7, 24, 16, 4, 10);
root [1]   UInt_t X0 = T0.Convert();
root [2]   TDatime T1(X0)
(TDatime &) Fri Jul 24 16:04:10 2020

``````

Sorry, if I write the line TDatime T1(X0); in my code I see nothing. Also, my question was how can I fetch the date and time in integer values from X0 to use them in my offline code e.g. to print them out. Thanks.

Yes, I see now. I just apply GetYear() etc. on T1. Indeed, it answers my question. Thanks, Elemer

Exactly. I mark this as solved.
PS: if you have a new unrelated question, please create a new post

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.