Patchset 0/5: Move TaskModel.daysBetween() and TaskModel.daysLeft() to DateUtil
Patchset 1/5: Copy TaskModel.daysBetween() and TaskModel.daysLeft() to DateUtil
Patchset 2/5: Replace usages of TaskModel.daysBetween() by DateUtil.daysBetween()
Patchset 3/5: Remove TaskModel.daysBetween()