Sample Code:

<apex:page StandardController="Opportunity">  
  
    GMT:   
    <apex:outputText value=" {0,date,M/d/yyy h:mm a}">  
        <apex:param value="{!Opportunity.LastModifiedDate}"/>  
    </apex:outputText>  
    <br/>  
    User Time Zone:   
    <apex:outputField value="{!Opportunity.LastModifiedDate}"/>  
      
</apex:page>  

Output:

For using apex:outputText tag use

<apex:page>  
      
    <table>  
        <tr>  
            <td><apex:outputText value="User Local Time Zone time is: {! NOW() }" /></td>  
        </tr>  
        <tr>  
            <td><apex:outputText value="GMT Time Zone time is: {0,date,yyyy.MM.dd G 'at' HH:mm:ss z}"><apex:param value="{! NOW() }" /></apex:outputText></td>  
        </tr>  
    </table>  
  
</apex:page>

Note:
<apex:outputText value=”{!NOW()}” />  – it will show GMT time.
<apex:outputText value=” {!NOW()}” /> – it will show time in your local time zone (note that blank space has been added before the left brace).