You can use an array to go through the times.

Create a struct with the fields time and temperature (you should think about saving time as unix epoch, meaning seconds since 1970, so that you save memory).

struct SetPoint {
    unsigned long time;
    float temperature;
};

Then you can declare an array of type SetPoint to hold the tubles of time and temperature:

#define DATA_SIZE  720
SetPoint data[DATA_SIZE] = {
    {<time1>, <temp1>},
    {<time2>, <temp2>},
    ...
    };

In the above, you need to replace <timeX> and <tempX> by your data. Then declare a position variable, which the element index, which will be invoked next:

unsigned int pos = 0;

We are starting with the first element (index 0) and compare its time to the current time. If it is equal (or current time is after the elements time), we will set the thermostat to the elements temperature and increment the position variable. Something like this:

if(pos < DATA_SIZE && current_time >= data[pos].time){
    set_thermostat(data[pos].temperature);
    pos++;
}

Note: I used the variable current_time here as standin for your way of getting the current time, and the set_thermostat() function as a standin for your way of setting the thermostat. Also I inserted a check into the if statement, to prevent the code going further, when it reached the data array end.

That said, depending on the used board you can easily get into memory trouble here. An Arduino Uno does not have enough memory to save 720 of the data points above. float and unsigned long both take 4 bytes each, so 8 bytes per element, which makes 8*720 = 5760 bytes. The Uno only has 2048 bytes total in RAM. There are enough boards, which have more RAM. The ESP32 for example would have way enough (though there are many others; the ESP32 is just the first to get into my mind here).

Or you can add an SD card module to your build and save the data points in a file. That would also make it way easier to get the data in your project or change the data. It would just involving writing the corresponding file on your SD card.

Then the workflow would be a bit different. Lets assume you save one data point per line as text:

• Open file and read one line. Close file.
• Parse read text into 2 variables (time and temperature)
• Use these variables for the if statement from above
• if the time of the loaded data point was reached, open the file again, read the next line and parse it into the variables
• The if statement now uses the next datapoint

and so on. If there is no line left to read, you could go into an infinite loop, stopping the code from running further than your data.

There are ready to use SD card modules to buy out there, and you can find many tutorials about how to use them online.