You could be cutting your chances of getting exposure on twitter in half depending on when you post your tweets so we looked at the research, the timezones and discovered some very useful information. 

Most of the research is USA derived data. I'm going to assume for the most part that in New Zealand and Australia we behave similarly when it comes to Social Media usage. But I will do my best to adjust relevant times for the South Pacific.

The 2009 "State of the Twittersphere" report from Hubspot had some interesting data. This first graph shows the number of tweets per hour of the day. Note this is USA PST time but note the spikes around 9am, 4pm and 11pm

So this suggests people are checking their twitter accounts as they start work, before they leave work and then after dinner and putting the kids to bed.Comparing USA PST to NZT we can see from here that 9am PST is 6am NZT the following day. USA 4pm is NZ Lunch time and Dinner time for NZ is almost bedtime in the USA

This graph shows the number of tweets per day. Its pretty clear that most people tweet the most while at work. Monday is pretty light to so Tuesday to Friday is when the action is. This translates to in NZ to Tuesdays to Saturdays if you are aiming for mostly USA based attention, traffic.

According to this article Tweeting at 4.01pm PST is the ultimate time. That is 1pm NZ time and 7pm EST 

At 4pm-5pm, 56% of Twitter users are looking at tweets, but only 39% are sending them - a margin of 17%.As a proportion of all tweets, use of the term RT (for retweet) is highest at 4pm 

The main peeks in reading seem to be as people arrive at work (9-10am), around lunch (12-1pm) and towards the end of the working day (4-5pm). There's a smaller peak later - after dinner perhaps. The interesting thing is when the biggest differences are - when people are more likely to be reading, and less likely to be tweeting. This difference is 20% at 11-12am, 19% at 12-1pm, and 17% at 4-5pm
 
According to this article it looks as though posting any time from 9am to 3pm will give you the best chance of getting exposure and traffic from twitter. Applying this to New Zealand thats anytime from 6am to Midday thats a great time for you to be posting content to get maximum views in the USA.

To back this up Fast Company wrote this post  which again shows that 4pm is a top retweeting time of the day. 4pm EST equals 10am NZ and 1pm PST which is still within that afternoon period of higher activity. Certainly looks like the morning is a bad time to get retweets as most people are either just reading or busy doing actual work.
 

 
If your distribution of followers is truly global then you might consider repeating key tweets 3 to 4 times again spaced 8 to 12 hours apart. That's a Guy Kawasaki tip published on Techandlife.com and its worth a read.

So lets wrap this up, here's a few key points;

• 10 to 11am Friday and Saturday are the optimal times to tweet if you're in Australia or New Zealand targeting retweets in the USA on EST or PST timeszones
• Most people tweet while they are at work, so thats a good rule to follow, and then again after dinner.
• More reading is done than tweeting 11am to 1pm and again from 4-5pm
• I'm making the assumption that the active times in the USA and the UK are the same in NZ and Australia so 9am, 1pm, 4 -5pm and 8-10 pm Monday to Friday
• If you're in the USA wanting to attract the attention of NZ or AU you'd want to tweet at Noon PST to get our 9am check in, 3pm for our Lunch time and 7pm to get us before we leave work for the day. When you get home and finish tea tweeting at 10pm to 11pm it will be just at the start of our evening action.

Justin Flitter is a Mentor at Flittermedia.co.nz