How MySQL Uses Indexes

[Mola Ji]

I create a table as follows:
CREATE TABLE IF NOT EXISTS `t` (
   `id` int (11) NOT NULL AUTO_INCREMENT,
   `i` date NOT NULL,
   `o` date NOT NULL,
   PRIMARY KEY (`id`),
   Index0 KEY `` (`i`)

)
to test the performance of my query I do:
explain select * from t o Where> '2013-05-04 'and i <'2013-05-11';
I got the following output on my local computer:

| select_type | table | Type | possible_keys | key | key_len | ref | rows
+ ---- + ------------- + ------- + ------- + -------------- - + ------ + --------- +
| SIMPLE | t | range | a, b ​​| b | 3 | NULL | 84 | Using where |
+ ---- + ------------- + ------- + ------- + -------------- - + ------ + --------- +

While on a remote server, I get:

| select_type | table | Type | possible_keys | key | key_len | ref | rows
+ ---- + ------------- + ------- + ------- + -------------- - + ------ + --------- +
| SIMPLE | t | ALL | a, b ​​| null | 3 | NULL | 84 | Using where |
+ ---- + ------------- + ------- + ------- + -------------- - + ------ + --------- +

This means that MySQL uses the index locally, but not on the remote server. Why?