Is it okay if the Input Voltage and Current are : 12V 1.2A

I'm using the Arduino UNO and SM5100B-D as my project. Recently I've been able to use it with the external power supply which maximum, able to give 12V and 1.2A... Along these testing days, I don't see any problems with it and both of my board are working perfectly... But, as my concern, is it okay to use it for 24 hours, 7 day/week??? I just need to use it for 12 - 15 hours per day.. So anyone who have the knowledge or what is good/not or even if it's healthy to use, please reply me a.s.a.p....

If your stuff attached to the arduino don't draw very much current 12V will be fine on a permanent basis. A few 10's of milliamps and the onboard regulator won't get very hot. A few hundred milliamps is a different story. The Arduino on its own will pull about 20-30 mA

kaizokudankaiser: I'm using the Arduino UNO and SM5100B-D as my project. Recently I've been able to use it with the external power supply which maximum, able to give 12V and 1.2A... Along these testing days, I don't see any problems with it and both of my board are working perfectly... But, as my concern, is it okay to use it for 24 hours, 7 day/week??? I just need to use it for 12 - 15 hours per day.. So anyone who have the knowledge or what is good/not or even if it's healthy to use, please reply me a.s.a.p....

The Arduino should be OK (I don't know what an "SM5100B-D" is, though); the regulator may get a bit warm (as it needs to drop 12 volts to 5 volts, dumping 7 volts as heat - its a linear regulator, so isn't very efficient - so you may notice the board getting warm - the regulator uses the PCB as the heatsink - if you can find a small heatsink and can superglue it on the regulator, it will help). If you are concerned about the heat, then use a lower voltage power supply (a 9 volt power supply capable of supplying 1 amp would be perfect).

Something else to keep in mind - power supplies are "sources" of current, while devices like the Arduino are "sinks" of current; in other words, the Arduino (and other parts) will only draw as much current as they need, and "no more" (note that as things approach zero resistance, current consumption tends toward "infinite"); thus a device rated at a current consumption of "500 mA" will only ever draw, at max (unless something weird occurs, like a short) 500 mA - even if the source of the current is 1000 amps or more (I wouldn't recommend playing around with such a power supply, though - but in reality this is correct; for instance, you could power your Arduino off a 12 VDC car battery - which is easily capable of sourcing 200 amps or more).