in this regard , diurnal computing refers to computing during daily cycles particularly in relation to ambient light available during different times of the day . computer systems , particularly mobile computer systems , may be used in locations that have differing amounts of ambient light based , in part , on the time of day the computer system is being used . some computer systems include lighting devices that illuminate input devices such as , for example , keyboards in the system . the light from the lighting device assists a user in operating the input devices . computer systems also include displays , such as , for example , liquid crystal displays ( lcds ) that have backlighting that may be adjusted for viewing . different ambient light levels may make some backlighting settings uncomfortable . it is desirable for a computer system to determine ambient light levels and adjust settings of the display and to turn lighting devices on and off depending on the determined ambient light levels . fig1 illustrates an exemplary embodiment of a block diagram of a computer system . the computer system includes a processor 102 communicatively linked to the internet 116 , a memory 108 , a system clock 114 , and an input device 106 . the input device 106 may include , for example , a keyboard , a mouse , or other similar input devices . the processor 102 is also communicatively linked to a display device 104 . the display device 104 may , for example , be a lcd display , or a cathode ray tube type display . an ambient light sensor 112 , such as , for example , a photoresistor , a photoreceiver , and a photoreceptor diode is communicatively linked to the processor 102 . a lighting device 110 such as , for example , a light emitting diode ( led ) is also communicatively linked to the processor 102 . fig2 a illustrates a front view of an exemplary embodiment of a computer system 200 . the embodiment of the computer system 200 is a portable computer system including the display device 104 in a housing portion 202 . the input device 106 is a keyboard that may be , in operation , illuminated by the lighting device 110 , located in the housing portion 202 . fig2 b illustrates a rear view of the computer system 200 including an ambient light sensor 112 . the ambient light sensor 112 may be located in a position such that light from the display device 104 does not appreciably effect the sensing of ambient light in the environment . fig3 illustrates a block diagram of an exemplary method of operation of the system 200 . the method starts in block 302 . the start may be initiated , for example , upon a boot - up of the system 200 , an exit from a “ sleep mode ” of the system 200 , or during operation of the system 200 . in block 304 , the system time is determined from the system clock 114 ( of fig1 ). the local time may be determined in block 306 . the local time may be determined by a user input designating the location of the system 200 , or from another source , such as , for example , the internet 116 using the network time protocol ( ntp ). the determination of the local time allows the processor 102 to determine whether the system 200 is operating at night or during the day . the determination allows the processor 102 to estimate the ambient light from sunlight that may be present in the system 200 operating environment . the ambient light sensor 112 may also send a signal to the processor 102 that may be used to determine the ambient light level in the system 200 environment . the signal from the ambient light sensor 112 may be used with , or independently to determine ambient light in block 308 . the determined ambient light may be compared to an ambient light threshold value 311 to determine if the ambient light is low ( below the ambient light threshold value 311 ) in block 310 . if the ambient light is low , the lighting device 110 may be turned on in block 312 to illuminate the input device 106 . additionally , the display device 104 may be set to a low ambient light setting in block 314 . the low ambient light setting may , for example , be a lower amount of backlighting than would be used in a brighter ambient light environment . in block 316 , a low ambient light routine may be started . a low ambient light routine may , for example , be a number of macros defined by a user that initiate particular settings desirable in low ambient light , or during a particular local time . additionally , a low light routine may include starting particular programs that are desirable during operation in low ambient light environments such as , for example , particular types of music , opening particular internet websites , or starting productivity software . if the ambient light is not low , and is above the ambient light threshold value 311 , the lighting device 110 may be turned off in block 318 . the display device 104 may be set to a high ambient light setting in block 320 . a high ambient light routine may be started in block 322 . the high ambient light routine may be similar to the low ambient light routine , however it includes settings desirable in a high ambient light environment . the use of local and system times along with the ambient light sensor , offer the system 200 the ability to operate with diurnal settings reflecting operating times and ambient light in the operating environment . these elements offer flexibility and ease of use to the system 200 . while the preferred embodiment to the invention has been described , it will be understood that those skilled in the art , both now and in the future , may make various improvements and enhancements which fall within the scope of the claims which follow . these claims should be construed to maintain the proper protection for the invention first described .