Python 2, 231 222 216 202 197 193 190189 bytes
i=__import__
t=i("datetime").date.today()
y=t.day
d=[(((`x`,"[ ]")[x<y],"[@]")[x==y],`x`)[t.month<12or y>25]for x in i("random").sample(range(1,26),25)]
while d:print' '.join(d[0d[:5]);d=d[5:]
-3 with many thanks to @AZTECCO
Examples below use an earlier version of the answer but the formula is the same.
Before December: Try it online!
December after 25th: Try it online!