# 1.
hledger -f - register --date2
<<<
2009/1/1=2010/1/1 x
  a  1
  b
>>>
2010/01/01 x                    a                                1             1
                                b                               -1             0
>>>=0

# 2. -b/-e/-p match the secondary date if --date2 is present (also, the secondary date is displayed)
hledger -f- register -p 2014/1/2 --date2
<<<
2014/1/1=1/2
  (a)  1

2014/1/3
  (b)  1
>>>
2014/01/02                      (a)                              1             1
>>>=0

# 3. date: matches the secondary date if --date2 is present (on the command line, at least)
hledger -f- register date:2014/1/2 --date2
<<<
2014/1/1=1/2
  (a)  1

2014/1/3
  (b)  1
>>>
2014/01/02                      (a)                              1             1
>>>=0

# 4. date2: matches the secondary date
hledger -f- register date2:2014/1/2
<<<
2014/1/1=1/2
  (a)  1

2014/1/3
  (b)  1
>>>
2014/01/01                      (a)                              1             1
>>>=0

# 5. you need to add --date2 if you also want the secondary date displayed
hledger -f- register date2:2014/1/2 --date2
<<<
2014/1/1=1/2
  (a)  1

2014/1/3
  (b)  1
>>>
2014/01/02                      (a)                              1             1
>>>=0

# 3. date2: matching is not affected by --date2
hledger -f- register date2:2014/1/1 --date2
<<<
2014/1/1=1/2
  (a)  1

2014/1/3
  (b)  1
>>>
>>>=0