Unfortunately I don't know Jane. All I do know is that the reports are that the police have some sort of indication that the murder occurred between those times in Wallaroo, NSW.
"It’s then alleged Holdom killed Khandalyce while on the way to South Australia in the vicinity of the small NSW town of Wallaroo some time between 2.17am on December 19 and 12.52am on December 20. Police have not released how or exactly where she died."
http://www.dailytelegraph.com.au/news/nsw/body-in-suitcase-daniel-james-holdom-charged-with-killing-khandalyce-stevenson-and-her-mother-karlie/story-fni0cx12-1227645596184
http://www.smh.com.au/national/dani...h-murder-of-two-year-old-girl-20151214-glnnik
The SMH article doesn't specify where she was killed, other than in NSW.
"in the vicinity" makes me think of phone pings i.e. a very broad area. However, if there is no mobile reception, I don't know what else to suggest, other than landline phone data of a specific place. But then again, what does "in the vicinity" mean exactly? Just outside, near the next town, on the outskirts? I can't fathom. From Google Earth, Hall is around 4 clicks from Wallaroo. I'm wondering about the pub at Hall. Does it have accommodation, for example? Is there something with camera footage? Would camera footage still be kept after that length of time? There has to be something that pinpoints those times, but I just can't think what else it may be.
Edit: I'm also wondering if there's any significance that both Karlie and Khandalyce appear to have been murdered on a day which falls on a weekend. Coincidence?