There is a build-in function DateQ. It is a very nice function. For example it knows that 2000 is a leap year, but 2100 is not

Needs["Calendar`"]
DateQ[{2000, 2, 29}]
DateQ[{2100, 2, 29}]

True

False

Now you can implement dateTimeQ

dateTimeQ[{h_, m_, d_, hour_, min_, sec_}] := 
  MatchQ[{h, m, d, hour, min, sec}, {__Integer}] && DateQ[{h, m, d}] &&
    0 <= hour < 24 && 0 <= min < 60 && 0 <= sec < 60;
dateTimeQ[___] := False

and convert

convert[quants : {{_?dateTimeQ, _Integer} ..}, prices : {{_?dateTimeQ, _Real} ..}] /; 
  Length@quants == Length@prices := OK;

quant = {{{2012, 1, 1, 9, 30, 7}, 150}, 
         {{2012, 1, 1, 9, 30, 12}, 130}, 
         {{2012, 1, 1, 9, 30, 33}, 470}};
price = {{{2012, 1, 1, 9, 30, 7}, 1.50}, 
         {{2012, 1, 1, 9, 30, 33}, 1.30}, 
         {{2012, 1, 1, 9, 30, 33}, 4.70}};
convert[quant, price]

OK

There is a build-in function DateQ. It is a very nice function. For example it knows that 2000 is a leap year, but 2100 is not

Needs["Calendar`"]
DateQ[{2000, 2, 29}]
DateQ[{2100, 2, 29}]

True

False

DateQ can take hours, minutes and seconds, but it ignores their values. See definition (there is no Calendar`Private`r in the rhs):

DateQ[{Calendar`Private`y_, Calendar`Private`m_, Calendar`Private`d_, 
   Calendar`Private`r___}, Calendar`Private`opts___] := 
 Module[{Calendar`Private`cal = 
    Calendar /. Flatten[{Calendar`Private`opts, Options[DateQ]}]}, 
  Calendar`Private`dateQ[Calendar`Private`y, Calendar`Private`m, 
  Calendar`Private`d, Calendar`Private`cal]]

However you can implement your own dateTimeQ

dateTimeQ[{h_, m_, d_, hour_, min_, sec_}] := 
  MatchQ[{h, m, d, hour, min, sec}, {__Integer}] && DateQ[{h, m, d}] &&
    0 <= hour < 24 && 0 <= min < 60 && 0 <= sec < 60;
dateTimeQ[___] := False

and convert

convert[quants : {{_?dateTimeQ, _Integer} ..}, prices : {{_?dateTimeQ, _Real} ..}] /; 
  Length@quants == Length@prices := OK;

quant = {{{2012, 1, 1, 9, 30, 7}, 150}, 
         {{2012, 1, 1, 9, 30, 12}, 130}, 
         {{2012, 1, 1, 9, 30, 33}, 470}};
price = {{{2012, 1, 1, 9, 30, 7}, 1.50}, 
         {{2012, 1, 1, 9, 30, 33}, 1.30}, 
         {{2012, 1, 1, 9, 30, 33}, 4.70}};
convert[quant, price]

OK