Migrate ES 1.4.4 to ES 2.4

[TTNarendran]

Hi Team,
Please find the mapping in 1.4.4
{
"sample": {
"dynamic_templates": [
{
"template_default": {
"mapping": {
"fields": {
"raw": {
"type": "string",
"index": "not_analyzed"
}
}
},
"match": "*"
}
}
],
"_timestamp": {
"enabled": true,
"store": true
},
"properties": {
"@context": {
"properties": {
"name": {
"type": "string",
"fields": {
"raw": {
"type": "string",
"index": "not_analyzed"
}
}
},
"school": {
"type": "string",
"fields": {
"raw": {
"type": "string",
"index": "not_analyzed"
}
}
}
}
Need to migrate to the 2.4.0 , kindly help me to modify the _timestamp field to date.